Not groups of mobs you can readily see, but things like spawn-ins or walk-ins. If you're set up and expecting trouble, you don't have problems. But, if you're, for example, looting something and the loot spawns a giant evil tree or a bunch of smaller evil trees, and you weren't expecting trees, you're going to have your face kicked until you can throw down your totems. Same thing for bosses that summon, big monsters on patrol, etc. While that can be said for a lot of things, Shaman mechanics can be unforgiving around this. You have some oh shit buttons, but Macross Missile Massacre isn't one button away.