Melee/missile mastery modify the effective skill of your weapon ranks. Independently, smite bonuses "offensive factor" (i.e. accuracy and damage) without modifying actual ranks.

100 polearms + 200 melee mastery = ~150 polearms (plus a possible 20 ranks from RW), then smite bonuses accuracy and damage on top of that.

Note that's just an example for easy demonstration, the percentages aren't meant to indicate actual in-game damage formulas. To answer your question, I doubt Smite directly uses melee mastery in the to-hit calculations, but it could be helping you out indirectly, with some restrictions.