Insenate Rage - he need a good backup - Bloodsecrator and Wrathmongers for additional attacks because his damage (
D6) is unpredictable. I remember a battle where i roll three "1" for damage in one turn.
Unfettered Fury - I can`t say much about him
Wrath of Khorne - as for me - best option (nice command ability, missile attack and re-roll to hit rolls vs monster and hero unit.
Skarbrand is something different. He is
CC monster but without wings he`s quite slow fire-magnet
There is also homerule in some shops which ban special characters.