For Wizards, nothing comes even close to Firebird 6 piece + Blizzard Apocalypse + Blackhole Blazar + Mammoth Hydra. The Furnace is BiS but that's crazy difficult to get. Second place is for a good rolled Sunkeeper + Magefist. If not, Maximus.

But is not just cast and forget. Firebird set needs to hit 3000% damage in 3 secs in order to proc the infinite DoT. And since this damage only cares about base damage, a slow 2 hander with high DPS is the best choice in order to hit that 3000% damage fast. If not, u will have to keep reapplying the DoT. That's why some ppl use Meteor Molten Impact so they hit that 3000% damage instantly and the DoT will tick forever.