I think Zoro overtakes Luffy as far as endurance goes going by feats.. But then again Luffy's G4 fuses Armament with his elasticity so he negates most damagePurely based on feats we've seen
1. WB (no explanation needed)
2. Akainu (after taking all them quake punches I'd say he's very tanky)
3. Jozu (as long as he doesn't face strong cutting attacks that can cut diamond)
4. Doflamingo
5. Luffy (Gear 4)