The “whoosh” sound effect to let you know when enemies are attacking you from behind is extremely late or missing since the update before Grail Knight. The sound effect either fails to play entirely (seems to happen most often with Stormvermin attacking from behind) or the whoosh sound only plays for a split second before getting hit, completing the rest of the sound effect long after the hit has already occurred.
Play any map, any career. Whoosh is late about 50% of the time, and missing entirely about 25% of the time.