Blazing Shield Templars used to be able screw with bombers quite a bit. Maybe a sorc negate tank or something? I don't really know anymore since I haven't played for a while, but a couple of stam sorcs with negates definitely could be annoying.
If the ballgroup is in open field or at a resource, just ignore them and go somewhere else. You won't find a better counter anywhere in the game.
The real problem starts when these pests somehow end up inside one of your keeps, especially if they're in the inner... can't leave them alone because they will flip the flags if you let them.