I have been doing a quest in The Maw Words of Warding a couple of days ago as my Warlock (Affliction at that time). When I was under the influence of that Assassin’s Soulcloak I was supposed to be invisible and should not attract any monsters in there until I disarmed a trap.
I think there is a bug. The cloak did not seem to work on my pet because it was pulling everything around and I don’t think it was the problem of being too close to monsters. I think my pet did not get invisibility.