It's okay, but I think 2 bosses were fairly poor designed, the dog and the robowars encounter.
The dog's "hide" mechanic is absolutely unintuitive, because it's not LoS based, it's based on how close you are to the crate. The new crate also spawns way too soon after the wave, often causing to spawn right inside the old one (even if everyone madly dashes away from it) and worst of all, you can break the crate spawn mechanic if you use an immunity effect (like for soaking the pounce). Having a single pounce aoe charge a box to max heat capacity is also just a dick move to bait some early wipes (given the encounter design it would have made more sense if gave a charge equal to one wave tick) out of people.
Same for the robowars encounter, the blades on the ground suggest that you can dodge them by not getting hit, in truth the blades have a more or less random hitbox (sometimes uneffected by them, sometimes they hit you even if you are 4 yards away).
They were by no means hard, the implementations of the mechanics is just piss poor imho. I also found the whole "let's clear another boss arena" thing a bit tedious. That was just unneccesary.
Fairly certain it will be the new hate instance for m+ though .