Not much of an exploit, but I'm pretty sure it's not intended.
If you have Subterfuge talent as a rogue, you can cast Mass Resurrection while stealthed. This has helped me numerous of times while world ganking with my friends.
Pretty sure there might be even more uses for thisHave fun!
Edit:
Just found out about another Amazing use for this.
You can start capping flags like in AB, without being visible. Even the animation wont show up while you're capping it.
Tested it in RBG and it can fool a lot of people who dont know about it.