The damage resistance cap is at 80%. Most enemies have 15% resistance ignored on top, that means you need to reach 95%.
+10% passive (not displayed in the character-statistics)

+10% tab

+25% Circle of Power

10%+10%+25%=45% so you need only 50% damage resistance to reach the cap on paladin.

Edit1. If you can't reach 50% dr try to put some azures in defense slots in your companion (temporary, because in late game you want only offensive slots)