But you said anyone. Not everyone. See my signature.
Again I see nothing here to prompt yet another whine thread inspired by either you or monique or some other random agent I've never heard of. All of the issues which you state are issues for most, not unique to Agents at all. Get called while teamed? Then you die unless you have a doc with you. Get called (thus implying 2+ people attacking you) when alone? Then er, die? You'd die less if you had a completed toon, you know those snare perks work incredibly well for separating a duo.
No, but it is easily better than a lot of other defenses available in the game.
It isn't that hard for an Agent to reduce the number of professions who can alpha them in 8 seconds to er...Shades.
Yes yes, debuffs. I forgot they all have Target == Agent on them.
Anyway enough of a derail on the "Agents are nerfest" wagon train with an idiot for a driver. I see no reason why this perk shouldn't be able to be queued from sneak and unsneak you when it lands. However I also see no reason why any offensive perk should be able to be used when not in combat.