Yea Melee in Onslaught is like getting sucker punched. It hurts and the pain comes unexpectedly, especially with desyncs. You really have to out level and grind content before facing tough bosses. I used to find boss encounters tough, but races have taught me to play much better. Kole and Brutus are not horrible with enfeebled and decoy totem, and even easier with skeleton totem, but I stopped using skeletotem, except on my summoner as it feels like cheating.
With that said I'm sure I'll die in Onslaught. The hard part will be the rares or maps that have damage and speed bonuses on top of the Onslaught attributes
With that said I'm sure I'll die in Onslaught. The hard part will be the rares or maps that have damage and speed bonuses on top of the Onslaught attributes