If you are going to have a move that has such a short range coming from a "stealthed" player then it should go off when triggered every time. Not have the attack cancel and you be brought out of "stealth" because the enemy moved less than half a foot to the left.
I really like this game. I want to love it. But this power along with the sluggish and nearly unresponsive controls have me frustrated to where I actually had to quit playing or else I would be one of those kids throwing a tantrum and destroying their computer on the internet.
Nothing is more infuriating than controls that do not respond to input. It may be because I am old and my reflexes are not what they once were, but the block/parry/dadge mechanics in this game feel so horrendously slow it is infuriating. Especially when the enemy gets heavy attacks that go off in a fraction of a second that flinch you and make you unable to respond to any follow-up attacks which regularly leads to being comboed from 100 to 0 with no input from the player registering at all.