Chaosmancer
Legend
Even with seeing the dice there's no guarantee that lucky turns a blow into a miss or even a crit into a non-crit. There's just a better chance of it happening.
I agree there is no guarantee, but it helps prevent a player from spending a point to re-roll when they see you rolled a 2, and then replacing your 2 with a 10 by accident
Sure, the rest (and better portion IMO) of the feat is still unaffected, but it would bother me to not be able to see what roll I'm trying to change