I usually just use a thunder>sleep on targets and then focus on one. Thing is from what i have seen so far is if i try to aoe groups of enemies i end up having all the agro and in turn have to start healing myself.
I know Archer you get an ability to reduce hate but have found leveling Archer very boring.
So 3 or more targets it is best to just aoe? Like say Ice2>Ice2>Fire3