No, it is game mechanics.
Look at WoW’s cinematics for what WoW combat unburdened by the limitations of a video game engine and game balance looks like (neither of which should be a factor in RP either).
It doesn’t look like /duel at all. A good example of a duel among the cinematics is Thrall vs Garrosh - you have Garrosh the arms warrior fighting Thrall the enhancement shaman, except the enhancement shaman uses a single onehander, very little magic, wears plate oh, and much of the fight consists of fisticuffs. And the shaman wins anyway.
I also didn’t see Garrosh performing the correct colossus smash > mortal strike > overpower rotation and then waiting for resets.