I almost feel like Ninja's need it in there present state and it would be great for bards as-well. I think Rangers would make great use of the skill, because lets say a 5 block radius, it would make them much more capable of defending themselves if caught in a jam. I'd much much prefer this over root coming back to the rangers. I wouldn't mind Beguiler getting it as-well. Theives could be a very powerful and GREAT class, not OP, but great class if they got this skill. They could sneak up behind the player, shed his armour and backstab him to smithereens; hypothetically of course.
Rogues are generally squishy. Why not give them a few edge moves to help them along in there quest for hard hitting sneak attacks?
I almost think it's a must on rogues as they are now. They drop WAY to easily when fighting Warriors. I was a Ninja last map, I can only imagine the horror it must be to fight a dragoon, paladin or dreadknight right now.