It's all about heroics. The larger locks lock seed packs can pump higher dps. I'm still able do 1500 on bosses on one target on my lock, as long as the tank is able to hold the threat.
Yes, if you have the right pally tank, well-equipped, and a lock with large pulls, then every member of your group can be a carry for all bosses with the exception of you. Hunters will be smoked, as are mage too unless they're weak and the mage will snipe at them before the seeds start to go off.