I also do exactly that with my 5 mages team.

/focus is on the leader, and each mage has a different target for sheep, assigned through the leader. They can cast normal spells aimed at /focustarget without changing target. However, they change target if I use the wand aimed at /focustarget. Pretty much like hunters do with autoshot. So it is sheep or wand. I use wand fairly often to finish off an almost dead mob.