They aren't meant to work the way they do atm, so they are simply broken. Not 100% of them but a really large number and this shouldn't ever happen. It's okay, when a boss has a bugged ability or whatever but not multiple bosses being broken, one-shotting you for no reason or having an enrage timer, that is probably set for 8 people not for 4.
That is just exaggerating. Except for the bosses I already mentioned there are no bosses that one-shot for no reason or have enrage timers that aren't possible to beat with a normal setup. While I would probably agree with you a few days ago, after having done them a few more times and discovered more tactics and mechanics what you're saying is simply not true.
Just today we figured out ways to deal with both HK in emperors betrayal and the third? boss (the guys that spawns waves of adds) in Battle of Ilum in consistent ways, bosses which we previously had struggled with. We have beat the last boss in boarding party easily the last few days, and got Bulwark on our second try and Mentor on our first today.
Although it's probably too late I'm not listing these to brag or something, but to let you know that with the right tactics and good execution all of these bosses are possible to beat consistently. Do I think we're doing it the way we're "supposed" to ? No. Do I agree that a lot of these bosses are over-tuned ? Hell yes. But saying everything's broken is just wrong.