Never had it, but looking through PBFs, I think Kyaltaru and Nerif are the only bards who have (outside of unpublished ones). Nerif had 27 Pks by 40, so that probably helps give an idea of the required number, since he only had 29 total.

Halting an occasional attack can be nice, but if that makes or breaks your success you're playing a bard wrong. There are so many far more important things to playing bards well than the edge. With lullaby & grand nocturne being what they are, and the player base largely knowing how easy it is to deal with those, preventing someone from engaging is probably more important for you being able to survive than it is for being able to kill people. Probably nice, but I can think of quite a few bard edges I'd rather have over that one, especially when you'll have less edge points in the current system.

It seems likely any area attack would bypass the edge, but I have no idea if that's the case.

Funny thing though, most players are never actually afraid of a bard that's alone in PK I'd say next to a healer, they are the least feared class in CF. And even a healer might be scarier since they have gate.