Not sure how exactly as I've not yet figured out how to replicate it but 3 times somehow when I come out of mist form I'm invisible not only to myself but other players. I tested by running through a group of AD without my eye closed and no one attacked me the 4 times I did it. I can also attack, which I did and based on them running around like angry ants flailing at the air, I'm assuming they could not see me either. I'm also invisible to myself which is kind of awkward for movement but the crosshair still remains.
Suspect combination of skills is some combination of being in stealth, cloak ability, and mist form. It appears as though somehow during that moment you switch from mist and your player is redrawn into the world, it simply isn't.