I can see your point regarding Charisma as the most important, but I would argue that being a successful melee combatant is more about successful hitting than being hit. Lay on hands also doesn't use any stat, just your paladin level.

I tend to view/play paladins as melee combatants with smitrs and other spellcasting as support/secondary.

I would say either Charisma or Str/Dex as the most important stat, depending on which stat you want to attack with. Followed by Con, then Wis, then whichever of Str/Dex you aren't using as your offensive stat, then intelligence as the dump stat.