Anyone noticed that every spell that is currently being cast will hit you if you guise during the cast? Say a warlock is casting Chaos Bolt on you - a good time to get out of dodge. So you Spectral guise, and it will finish its cast and path to you, critting your pants off even though you're now stealthed.
As you say indeed i get hit. The other thing, while intended, is that you lose it to dots instantly, as any damage to you break it. I'd like it to be 3 damage instances, so 1 tick of each dot would count towards that instace-counter. You'd lose the guise quick enough anyway but you'd still get a couple of sec breathing ground.