this is exactly what I am doing right now, I have 4 60 shamans sitting on rest XP (I play one AV a day with them and I am boosting a few classes I have never played before, plus a 5th shaman. From 1-60 you can boost them in sfk/sm/brd/strat without ever having to cast a single spell with them, although not sure what I'm going to do when I hit 60, guess I'll slowly rotate people around so I instance level 60-70.