I agree with the 3%, based on what the Tank Job brings to the table. If they bring next to nothing to help with the Party/Raid, then they should be on the top in terms of DMG output, because they would need it to compensate for their poor party/raid utility. Then the one that brings loads, would be on the bottom in terms of DMG, due to how much they bring to the group/raid in terms of useful utility.

So to me. (Highest to Lowest DPS Output.)

1. Dark Knight
2. Warrior
3. Gunbreaker
4. Paladin