I'm posting this on the xbox forum since that is the platform I play on, but I'm sure this is an issue affecting all platforms. The lucky prefix is increasing the critical meter 15% faster as it is supposed to, but there is no extra damage from critical hits being applied. I tested this with a lucky .44 and kellog's pistol with the same attachments on a super mutant warlord. A critical hit from both weapons did the same amount of damage.

edit: after looking around a bit more, it seems like better criticals might have something to do with this. It could be overwriting the extra damage lucky is applying instead of being combined in an additive or multiplicative way.