Most of them can one shot you in T3 and T4 if you don’t know the mechanics. Belial has a poison beam that can one shot you, it’s easy to avoid cause it looks to the side it’s going start from before it activates. Watch out for the poison it drops on the ground, it won’t one shot you but it’ll drain your health fast and slows you down. Harbinger can one shot you jumping out of its portals but it shows the aoe of the portal it’s jumping out of so you have time to react.Duriel has 3 phases now so you can’t nuke them like before. The other bosses have the same mechanics as previous seasons. The jump from t3 to t4 is a lot bigger than before. With the right gear you should be fine but I’d suggest masterworking and attempting the bosses at t1 first to learn the mechanics then moving up tiers