WoW: Why people think that paladins are overpowered class?

i have a lvl 85 paladin and always when i duel someone and win everyone was saying like of course he won he is a pally same in raids or other PvE's everyone was like of course he suvives he is a pally and i don't get it i don't see anything overpowered in pally's i mean warlock or frost mage can defeat me with no problems