I'll say this though.

For PvP purposes specifically. If THF and/or NIN get a Stealth like ability, I sure as hell hope it actually makes that person completely undetectable to anyone outside of your own party. With how directional focused combat is, I'm sure they'll implement a sneak/trick attack like thing for Thief as they did for XI as well, that's somewhat of a given. But this is just about the stealth.

Ah, to suddenly appear behind your opponents team's Healer and crit them for massive damage would be fantastic.