Yes, it's a bug.

Why immediately assume it's a bug? Perhaps quick battles operate under different principles. There are only two opinions here: either ban quick battles altogether or allow them without restrictions! Otherwise, there will be excuses like: "I forgot to turn off auto-battle, give me auto-battle" :D

P.S.: By the way, here's a funny thing: one Hydra takes a Hive without any losses, but if there are two Hydras (in one stack), one of them is lost :eek: I have no idea how to explain this.