When I use Sleep spell and switch target (happens when the mob resisted my Sleep spell or the mob was not within the Sleep spell radius, my companion simply turns into Healer mode (although the stance still says Free Style). Only way the companion will spring into action is when I continue killing the initial target without switching or when the initial target wakes up.

I am not sure if this is intended but I think the companion should attack the target which I use damage spells on. Good thing that the companion do not wake them up by hitting the slept ones.