I use WASD, and am not ashamed that my S is bound to backpedal. It's a good way to edge out of melee range of a boss, or interrupt a cast on my priest. But I don't backpedal away in PvP. At least I don't think I do. So I set S to screenshot and did some arena. Here's the results:
I think what happened here is that as I was strafing right, I healed myself (shift+R) and hit S and D at the same time while panning back to the left. I think a better movement would be to simply continue strafing. I also need to put Spirit Mend somewhere more movement-friendly so I don't have to stop strafing.
DK's were giving us hell. I swear I would get them to 1%, then their health shoots up and Vengeance kicked in with a vengeance. Still, I climbed to 1288 rating with a 8-8 win loss