The issue isn't just the bosses' health, it's how little there is to do in a boss fight. After a while of button mashing, you just want to get it over with.
Let's try taking in consideration why people don't like the high HP. I don't have the DLC but I can give a few stuff in after reading old threads about it when the DLC came out. People didn't like the high HP and one of their reasons is that it gets boring doing the same thing over and over and over again. What I mean is that if there is no objective that has to be done besides defeating the boss, it can get boring. It's not like FoS 2 last boss when you have to do whatever again with the power core, it keeps peoples minds going, so I can understand why people would complain. If there was something else that had to be done then maybe it wouldn't be the only concern or however you want to put it. After people get the gear for that DLC it does become easier yes and they have a better understanding but it can still be tedious for some.
I actually love the Boss health in some aspects, but the boss fight are boring (Except for LB AFTP) and you get no adrenaline rush.
Tell your DPS's to take off half their gear and spec half their skill points. Boom double HB on the boss.
Bingo. High HP bosses are fine so long as there is something interesting to do within the fight. These boss fights are the epitome of generic. There's nothing interesting about any fight outside of Artifacts last boss and Lockdown last boss. Controllers dump power and nothing else. Healers heal the tank and nothing else (everything else is a 1 shot). Tanks take the solo boss to a corner. That's it. Boss fights should be engaging and fun. There has to be a threat beyond the boss and there isnt. Mechanically these fights are bare. The ONLY challenging part of these fights are not messing up. A Tank can counter a boss successfully 9x out of 10, but give him immunity once and hes going for that artifact. These boss fights are a joke.
Tanks? Plural? You mean there's more than one? LFG: wanted, 1 tank and DPS only for A&B. must have supply drop - no healer, no controller run. Actually, that could be happening now....I don't pay much attention to LFG. But I do know that I want a healers, tanks and controllers in my groups.