1. Many people have reported loss of action bar during tactical combat. I've noticed that this occurs every time a hero (player or AI) casts a multi-target spell, e.g. mass curse, if the next unit on initiate is a hero then they will lose their action bar.
2. Units with magic resistance to single target spells are not resistant to multi-target spells e.g. resistant to curse but not mass curse.
I do hope we get a bug fix patch before the next beta.