If Vin new about Nicrosil they definitely would have been used in the siege of Luthadel. And if she'd found Nicrosil chances are she'd be looking for Chromium too, since that would have been hugely helpful against enemy allomancers, but even Nicrosil would have helped, she could have depleted all of Zanes atium the second he blocked her.
So was Vin, she didn't get boosted.
It's not a matter of allomantic strength he would've needed the technology and someone would almost certainly have found out, even if it was one of the inquisitors. Additionally unless he went out on mining expeditions himself he would've needed help, I don't think that he had more tech than AoL did.