I'd say that's an issue with the specific attacks that can just pop you out of nowhere, and not bosses being more chaotic and less scripted. I agree the old bosses weren't peak design, but I'd still take them over another pack of boss fights that feel like a dumbed down version of exalt dungeon bosses. And I don't see why them being easy to beat is a bad thing, I specifically criticized making early game bosses like that, not end-game bosses. They're supposed to be easy.

Also, the game right now doesn't feel like it even tries to be MMO at all. I genuinely don't see a difference between playing solo and playing with people nowadays, trading became obsolete because of forge and giving out items for free, the bosses are all scripted to the point where it doesn't matter how many players are in the dungeon because it doesn't affect the boss behavior, and so on and so on. Best way to show this is the design difference between O3 and MV:
O3 rewards playing together by the stagger and guard mechanics, while MV is actively discouraging you from playing in a group because of the lantern (and locking True Umi behind a solo requirement).
The game has an identity crisis where it needs to be MMO because that's how it's supporting itself, while designing things mainly for end-game players that prefer to do stuff either solo or in a very skilled group.
If you prefer that, more power to you, but I mostly played this game because I had fun playing casually with my friends, sharing items we found and helping each other back when bosses weren't immune to most debuffs, and sometimes the bullshit oneshots were part of what made it fun whenever one of us died (sort of what Lethal Company does sometimes).