I understand this question is a million years old, but I still can’t seem to find a way to strictly level it up. While I’m not focused on it now as I’m relaxing with Medic, and have other awards, I still don’t understand what exactly to do. One thing I may suspect is at level 3 regeneration from damage, maybe that’s where the xp comes from.
I’m on 360 patch 1.1, if that means anything.