Why the hate with endgame fights?

[Sebazy]

Exactly how I would have itwork.

This is pretty much how big MMO bosses used to work if you go back 10-20 years.

I'm not sure if it's rose tinted glasses or you simply don't know any better. But I can promise you first hand that it absolutely didn't make for 'better' bosses. At best, you had encounters that were slow and methodical, but more often you just ended up with painful zergfests where you had to grind a boss down before people gave up or were simply unable to raise fast enough.