I'm also experiencing this bug, I've noticed. Not the worst one I've encountered, but it's frustrating only for the fact that, after choosing say Aloth or Durance to cast a spell, they will just wait until I manually assign them to attack again, even though the other companions are getting beaten up. It can be worked around obviously - just have to be extra aware and keep assigning the team their actions. And it's still a lot of fun!