Raid Bosses do not belong in a 5v5 team game.
Champions should not be designed with the intention that they require 2-3 champions to take down no matter what. That leaves the team with no option for an even match against the rest of the enemies but to have a raid boss of their own as well.
And so they can't be beaten unless you're one yourself, or directly counterpick them. And even then, they still have only one weakness in their "immobility"-- something which is completely negated by Black Cleaver and Stormraider's Surge.
These champions need to fixed so that they don't have so much in-kit healing that it doesn't matter that they didn't buy any. No champions should be high damage and high defense before having the items to back it up because this is a PVP game. Against AI, that kind of character is fine because it gives you the option to play solo in an otherwise squad-friendly game. But in this game, they do not fit.
, the Devour of Outland
, the{ Surge of Northrend
The Sadness of Ahn'Qiraj
.... shreds to bit any raid boss from a comfortable distance, perma slows with rylais, dashes away if necessary, knocks them back if necessary or into a turret.