When you cast a channeling spell (e.g. as a warlock a drain or an aoe) or melee, it breaks follow. He wouldn't break follow with shamans unless he melees, because there's no channeled spells.

Just hit Alt+F to make them follow again

For pet attacks, make a macro (can be in game) that does something like:
Code:
/petattack
/startattack
/cast some shot