I don't understand your reasoning. Tanks are top damage on almost every fight, that doesn't mean the non tank equivilant is bad. Most people also do not include the tanks in their assessment of DPS since the tanks damage stems almost fully from vengeance, which to be frank is a rediculous ability.
On H Spoils for example, I was top DPS in raid "after" the tank. I did 371k the tank did 571k, that's a full 200k higher than me. It doesn't mean DPS warriors do badly or we "shouldn't bring one since the tank did more damage." If they replaced me with say another rogue who clocked in I think around 250k dps, we likely would not have met the timer.
I have a quick question for y'all, We are going for Heroic Spoils later today. Any reason to stay Fury or would it be better to go Arms.
Depends on the aoe dmg of the rest of your guild. We found it best to go fury for the insane burst potential+their cleave is still really good. Small/mediums adds should be dying fast.