Peronsally i think you should, i plan on doing 3 mages too myself because then i can do 3v3 arena on my own, pluse if u make the leader a frostie and the other 2 fires, u can keep the enemy at bay while also doing bulk fire damage, or you could just go 3 frosties and have massive shatters? i prefer going fire personally XD

basically the way i see it is that it only changes the end game stuff, so probably dont worry if u plan on playing casual and MAYBE making up to level 70, but if ur definately going to lev 70 i reccommend 3 mages