Since I seem to be on a roll when it comes to writing about companions, I might as well go ahead and finally publish this post, which I've been mulling over in my head for several weeks at least.
"Back in my day" is an irregular series in which I look at a particular aspect of the game and how it has changed over the game's lifespan of currently more than five years. Companions are an interesting case in so far as very little about them changed for the first four years or so, and then Knights of the Fallen Empire changed everything. But let's talk about one thing at a time.
Every class in the game gets to recruit five unique companions over the course of its class story, plus the ship droid, which is identical for all classes within one faction.
The first additional companion to be added to the game was HK-51 with patch 1.5 in November 2012. While his release coincided with the game's free-to-play transition, I thought it was quite obvious that he was still a product of the original exuberance with which the game had launched, when people were still having delusions about SWTOR getting twenty million subscribers and releasing massive patches every month. He had a fully fleshed-out companion story that you had to unlock by maxing out his affection, with slightly different dialogue for Republic and Imperial characters, and acquiring him in the first place required the completion of a lengthy and demanding quest chain. I wonder how many people even bother with it these days... I still think it's a great piece of content and I suspect that it's fully soloable now even where in the past certain stages used to require a group, but it's kind of hidden away, requiring you to go to Section X and talk to that random astromech droid in the base to start the quest chain.
In August 2013, HK-51 was followed up by Treek the ewok as part of patch 2.3. The effort put into adding her was already somewhat scaled back, with no great quest chain required to acquire her; you just had to buy her "contract", either with credits or Cartel Coins, and that was it. And while she also had a full repertoire of conversations she would have with you on your ship, some money was saved by having all her dialogue be alien gibberish. She must have worked out pretty well for Bioware though, as Damien Schubert cited "some months we sell ewoks" as an example of things going well for SWTOR that year.
After that, it was quiet on the companion front for more than two years - while the Forged Alliances story arc and Shadow of Revan introduced Lana and Theron as "quasi companions" during the storyline, they refused to actually join us in combat for the time being.
Until 4.0 that is, when everything was shaken up big time and all of our previous companions were taken away. They were replaced by a bunch of new story characters which were the same for everyone, and a promise that eventually we'd see our old friends again as well. This has been realised in part since then, though many companions remain missing. For those who remain somewhat bitter about this, it might be worth pointing out that before Knights of the Fallen Empire, it looked like our companions' stories might never be advanced again, as it simply wasn't feasible to focus on producing content that only a fraction of the player base would even see. For example continuing the story of Elara Dorne would only have been relevant to about 12% of players (those who play a trooper), and not all of those might even care about that particular companion. By cracking things open and slowly bringing those old companions back in a manner that makes their stories accessible to everyone, we do at least get to see them continue to participate in the ongoing story.
Of course we mustn't forget that Knights of the Fallen Empire also brought with it creature and droid companions as additions to the infamous Cartel Packs. There is something cynical about companions without any kind of personality or story being sold for money, especially when looking back at the rich backgrounds for companions that the game started with, but I can't deny that there's a certain appeal to these guys too. I, too, own an Akk Dog after all.
One argument in favour of having more companion variety used to be wanting to have different companions available to play different roles. It's easy to forget this now that any companion can play any role on the fly, but at launch companions were effectively limited to a single role. They had "stances" which could be used narrow down their behaviour a bit, for example by having a healer not worry about healing so much and just make them use their damage abilities, but this didn't really make a massive difference. A healer trying to do a bit of dps was still just a healer trying to do a bit of dps, as in: not very good at it.
In case anyone needs a reminder (or wasn't around back then), these were the original companions' trinity roles:
Tanks: Blizz, Bowdaar, Broonmark, Corso, Iresso, Kaliyo, Khem Val, M1-4X, Pierce, Qyzen, Scorpio, Scourge, Skadge, T7-O1, Vik, Xalek
Damage dealers: Akaavi, Andronikos, Ashara, Gault, Jaesa, Jorgan, Kira, Nadia, Risha, Rusk, Temple, Torian, Vector, Vette, Yuun, Zenith
Healers: Doc, Dr. Lokin, Elara, Guss, Mako, Talos, Tharan, Quinn
You immediately notice that there are a lot fewer healers than anything else: This is because every class was given one ranged tank, one melee tank, one ranged dps, one melee dps, and just that one healer. That seems like a sensible distribution on paper, giving everyone a little bit of everything, but in practice the vast majority of players just wanted to do damage while a healer kept them alive, which made for very disparate levelling experiences for different classes in terms of gameplay, depending on when they unlocked said healer. Levelling a bounty hunter for example was easy mode from the start, since your healer (Mako) was your first companion and even joined you on the starting planet, allowing you to go and solo heroic missions right from the beginning - back when this was far from trivial. The biggest contrast was probably the Jedi knight, who didn't get their healer until early chapter two, making the first forty levels with no heals and no crowd control a bit of a slog at times. Smugglers got their healer, Guss, even later, near the end of chapter two, but never felt quite as hindered by this due to having at least a bigger toolbox to work with while getting there.
HK-51 was just another dps companion in terms of his role, but Treek shook up the paradigm by combining both a tank and a healing role in her stances. To me, as someone who likes to tank and heal, that made her pretty useless as I usually wanted a dps companion most of the time, and that was the one thing she couldn't do. For most players however, that tank/healer combo was everything they had ever dreamed of, and Treek was quickly declared overpowered and superior to all other companions.
The ship droids, by the way, were also healers, and you might wonder why more people didn't use them while levelling up if they wanted a healer so badly and their class didn't actually get one until later in the game. The reason for this was two-fold: The first was that the ship droids had no personality or opinions outside the ship, making them boring to have around during mission conversations, but the second was...
At launch and up until 4.0, companions needed to wear full sets of gear just like player characters, unlike now, where they only really need to wield a weapon to be effective in combat and any dressing up, where available, is purely decorative.
For droids, this meant that they had to be equipped with a full set of "droid parts", which were hard to come by unless you had Cybertech as a crew skill and could craft them. While levelling, you would only very rarely encounter them as drops or quest rewards, and at endgame, you were stuck with the annoyance of the armorings in moddable gear pieces being bound to their slot, so that none of them could ever go into droid parts because no droid part was flagged as being the equivalent of a chest piece for example and therefore ineligible to receive gear pulled out of one. Every now and then Bioware would remember that hey, people wanted to gear their droid companions too, and added some new parts, but as a general rule of thumb their gearing was perpetually neglected until droid parts were finally removed from the game in 4.0.
For non-droids, gearing was a bit easier, but it still took work to not just keep your character geared, but five class companions on top of it. Most people just picked a favourite and focused on gearing that one. In pugs, this could sometimes lead to conflict when people used the requirement to gear their companions as an excuse to roll need on absolutely everything.
It was also a bit confusing though, because like players, companions effectively had classes, and back then, pre-Mastery, different classes needed different main stats (also see my "Back In My Day: Gear" post for this). It wasn't always totally obvious what a companion's class was though: For example Elara Dorne is a soldier in the story, but she wields a blaster pistol, something that neither of the trooper's advanced classes can do, and used to use small, trickly heals like a smuggler. The correct answer was to give her trooper gear, but was that truly obvious? Several other companions wielded weapons like vibroblades and electrostaves, which aren't commonly used by player characters, which could again leave you guessing.
If you didn't keep your companion's gear up-to-date, their decreased power would become quite obvious quite quickly, but even a companion decked out in full tier gear was noticeably weaker than a similarly geared player. Basically, having four real people in your group was pretty much always an advantage unless you had a really bad balance of classes and roles.
To me, this was most noticeable with healing companions, which were strictly limited in terms of how much burst healing they could do in particular, because using their biggest heal on you would place a relatively long debuff on you that would prevent you from being on the receiving end of said heal again. As a result of this, healing companions were at their best if they could spread lots of small heals around in a group - in fact, at this they were better than player characters even then, simply because their AI would allow them to react to even the smallest drop in anyone's health pretty much instantly. If you needed someone to keep you alive against a serious onslaught of damage however, nothing could replace a real healer.
The removal of those restrictions and the general buffs to companion power turned a lot of the game on its head in 4.0. There was a lot of debate leading to companions getting nerfed, then buffed again, then nerfed again (I think) - I honestly lost track. I don't have the exact numbers, but my impression is that they are slightly less powerful now than they were at the start of 4.0, but not by much. They are still powerhouses that make you cross your fingers that a member of your veteran flashpoint group with no healer will drop group so you can whip out a companion instead to make everything easier.
Interestingly, companion affection had no influence on a companion's combat performance originally, just on their crafting efficiency. Different companions also had bonuses when performing certain crew skills. This was also changed in 4.0, when companion "influence", which replaced affection, suddenly made a big difference to a companion's strength (and character-specific crafting bonuses were removed).
Another thing that's worth mentioning is that companion abilities were greatly homogenised with 4.0. I don't think Bioware ever intended there to be massive differences between different companions, but some of them had unique little abilities that gave them additional character and made them more fun to have around, such as Blizz's rocket launcher attack or HK-51's snipe ability. These were all taken out during the great revamp, much to the chagrin of many players... though I'll confess that I didn't pay enough attention to these to really care very much.
Companions have always suffered from having to straddle awkward lines. They were supposed to be colourful characters of the kind that made Bioware's single player RPGs so popular, but gameplay limitations prevented you from really having much of an effect on them story-wise - Bioware infamously allowed players to kill certain companions in the beta, but because people regretted it afterwards, players had to be saved from themselves by having that option permanently disabled.
The big 4.0 revamp was supposed to do away with some of these issues, but in my opinion mostly just traded them for others. True, being able to change companion roles on the fly meant that you weren't stuck with the default healer anymore, but with how much of a difference companion influence makes to their power levels and how much of it there is to grind, do you actually want to switch from the one guy you got to 50 to another one that may only hit half as hard? Also, while in the past you had a limited selection for different situations, we now have a plethora of companions... just to not really need them because whichever one we picked as our favourite can play any role anyway. I don't really miss companion gearing though, just staying on top of all of my alts is enough work as it is.
There is also a general tug-o-war on Bioware's end in terms of what kinds of companions to invest in. Add new ones as part of the story when creating new content? Bring back old favourites that people have been clamouring for? Add more funny-looking animals and droids to the Cartel Market? Players probably want all of the above, but with what resources?
My suspicion is that now that leadership seems to be doing a turnabout after KotFE / KotET, we'll see more of a return to old favourites in the near future. But where we go once we got all of them back (whenever that may be), will be anyone's guess.