Ironically it's the only character I've completed the challenge. I use my shield/revenge perks build.
1 arena - pure duel
2 arena - buff dmg, kill shaman then gladiator. Forward side heavy move is good to trow oppoents over and over again.
3 arena - playing def for revenge then spam zone. First i killed one shaman, then i try kill kensai and 2nd shaman in one time. I prefer right side of map (behind mobs)
4 arena - focus on white hp shaman,drop her hp to 1 segment. Play def until other will be near dead (bleed) ,use revenge and kill them all.
3 arena is nightmere but posiible in that case. Additional shield after revenge helps.
I have problme to complete this on other chars where i dont have this perks.
PS: sry for poor Eng