Hmm... let's see, there are a countless amount of such events for me. But two I remember well....
I was playing my Blood Elf Paladin who was at the time about 34, I was walking in Arathi Highlands heading to Stormgrade, why I odn't remember. This isn't exactly a world pvp story, but there was another Blood elf there, he was a 42 Mage. I decided to duel him, keep in mind he's 10 levels higher then me, well the fight was over pretty fast and I beat him with seal of command/judgement and such. I didn't have to use Divine Shield either before people start pally QQing.
On my Dreanai Shaman who was in the late 40s I was in a group for ZF. While waiting at summoning stone waiting for other group members to be ready for summons. I decide to duel the mage in our group who was 1-2 levels higher or lower then me I don't really remember exactly. The duel starts out he frost novas me, but he's standing right there so I swing at him, I was using a two-hander at the time, crit+windfury crits+Stormstrike+Earth shock, then the duel was over. The only damage I took was the small amount from the frost nova. During the instance I began dual wielding for the first time, after we were done with ZF I dueled the same mage again with pretty much the same results
So basically Mages are easy mode for me while playing Paladins and Shamans, except when they pull that water elemental BS.