I am not sure if it is completely linear and you yourself demanded to clarify the role of the real damage output in pvp.
So far the damage was constant and the (my) armor was changed. If the damage output is important (as in: the higher the damage, the less the reduction percentage f.e.) so could possibly the class factor in. Remember secondary stat perks are not evenly distributed over classes too. You only want to see tanks getting slapped by Rogues. Busted!