Boss HP too high ( their skills are ok )

I actually see both of your points of view.
And I'm the first to be saddened by the realization that DPS first is almost the only way to go, at least, for the first three acts.
My first encounters with the Count and the Perennial king was a disaster. I was wandering how in the hell I managed to even beat them.
When I watch other players (Rogue, Mercenary, Sorc), I was amazed to see them deleting those bosses before they even do some of their attack and the others not more than once or twice.....
No wonder that I was sweating with those same bossed going all out on me 5 times in a row.

Like you said, it all boils down to the passive tree. Literally. You are basically only be given the choice to go defence or offence (for the warrior at least) and if you chose defence, you gonna suffer as it has been mentioned above, you'll still get deleted by white mobs.

They won't be able to balance such a tree. But something needs to be done on survivability, because at the moment, investing in defence on the passive tree seems like a waste; And that inevitably leads to an already meta build for warriors at least. By design...

PS : The Forgemaster boss is a typical exemple of the issue. It's clearly a DPS check. GGG is forcing the meta early on at this point.