This AA appears bugged, and yes I've submitted an in-game bug report on it, just wanted to put something here in case anyone else looks. The AA is supposed to add a threat component to Shroud of Bertoxxulous, and if you examine the spell you see a new green line added saying 'Increases Threat to target encounter by xxx'. If I cast it on myself and go out and get smacked, I see the threat numbers procing when the Nihilistics damage procs, and I can measure the threat in ACT. However, if I cast Shroud on another player in the group, the Nihilistics damage proc still goes off, but the threat doesn't. Seems pretty clearly buggy. Would be nice to fix to help survival in dodgy pick up groups.