Moving here from
this thread.
It appears that in the Night Market, some enemies have bugged targeting - they cannot be targeted by heavy attacks, or light attacks for that matter. In my personal experience this happens in The Parch with the animated armour/knight enemies (with the purple effects), but also some others.
Furthermore, it appears player skills are bugged in NM sometimes too. For instance my ultimate (DK banner) activates, consumes ultimate, but doesn't actually appear. My character does the animation, but no banner shows up and it doesn't take effect either. Same with DK fire breath (engulfing dragonfire), and some other abilities. Some abilities, like heavy attacks, also seem significantly delayed as if the server was struggling, even though I experience no such huge skill delay in other group content like incursions, battlegrounds or group dungeons.