Yeah there are definitely some boss fights that they could have put more thought into. Starting ranged classes right next to elites at the beginning of a fight happens fairly commonly. Sometimes the boss will immediately knock you back 10-20 meters which is actually a cool way to start a boss battle, but more common is that you just have to expect a death and then come respawn and start the battle on your own terms. Rare but common enough to be an issue. Still.. dying should never be a viable strategy to approaching a boss fight.
I haven't had too much trouble fighting two strongs if Khem is my companion, since he can just take the agro from one and the second one can just get hammered down, even if it's attacking me, since Assassins get multiple "Oh shit" skills, but namely that 50% to defense one helps in these situations. I rushed the first planet after chapter one with my assassin to get the next companion and she doesn't seem that great so far, but at least I can finally play nice in conversations with my light side assassin character.
I definitely experienced this problem earlier today with my operative character that I made today after deleting my sniper. The end of Balmorra's imperial agent class quest has a boss that does that thing where he knocks you back 10-20 meters in the beginning of the fight. GREAT if you're a sniper, since you can just get up and get into cover and start shooting him, but as an operative it made me useless for the beginning of the fight since it was coupled with a slow. To make matters worse he has two AoEs. These AoEs will never, ever hit you if you're a sniper, since the only companion you have at that point will hold his agro perfectly. But when you have to get into melee range as an operative, he tears you the hell up. In any case, the fight starts after the conversation and I died and even when I respawned and got to start the fight on my own terms, I only got out with next to no hit points and my companion downed. On the other hand, I don't think my sniper took even 15% damage in the fight. The reverse is true often enough, but it can just be frustrating how inconsistent it all is.
On the other hand, I'm not sure if it's grossly imbalanced, it's just that based on how diverse the classes can be, building boss battles can be tough so they opted for some being real hard and some being real easy depending on your AC
In any case, my operative is my only dark side alt out of 7 (all 22-33) and I'm having fun with him. I really like Kaliyo and I'm basically playing dark side just to please her since I find her character so fun. She's a lot like Jack from Mass Effect 2 but doesn't appear to not so secretly just need someone to listen to her. This probably means she's a psychopath, but I still like her.