He is described as wise, far stronger than Garrosh, perfectly honorable, smarter than Tyrande, the High Priestess of the Temple of Elune and Leader of the Night Elves since 10.000 years and everybody likes him. He doesn't have weaknesses and is pretty much perfect in everything he does.
If their chest is harder than a thick breast plate that was forged for Archimondes Second in Command, also probably a masterpiece of the Legions smiths, they are pretty much overpowered.
Cairne doesn'T wear any armor of all. All Lothar had to do would be thrust his legs between Cairnes legs.