LOl ailments are OP, go watch RaizQT build where he fucks with ailments. He took down the first act boss before he could do any of his one shot moves. I think it matters what skills you chose because some like shock and ice dont really do ailment dmg. But the fireball, poison, and the aether stuff does so you can scale those up. He was one shotting packs with that aether void looking circle thing on the ground where it sucks up mobs to the center. Then the fireball was his go to for bosses and majors. Plus later on certain attacks can be switched, like that aether ray attack can be switched over to poison. There are probably others.
He wasnt really fucking with melee either just a pure caster, but you could pair a melee attack along with his builds for a hybrid and use some of those ailments too like rend.