A tanking class that doesn't at least have the ability to speed run is a bad tanking class. A tank needs to be able to handle both single mobs and large groups of mobs to be considered well-rounded, and I don't think that SE is going to skimp on either aspect for Dark Knight. I would't be worried; however DRK manages its MP, it's going to be able to keep up with what PLD and WAR can do.

The design of DPS aoe abilities makes it pretty clear that SE is not, and never has been, "against" speed running in the way some players are. With the exception of Flare and Bane (for different reasons), most DPSs' aoe abilities are designed so that four mobs is the MINIMUM point at which those abilities become superior to single-target attacks in terms of damage dealt. Each mob added on top of that greatly increases the total damage being dealt by the aoe. DPSs' aoes would have no purpose at all, if not for the expectation that tanks are going to pull more than four mobs at a time. SE built speed running into the game from the ground up.

Speed running isn't the only way to run a dungeon, but if the players are skilled and geared enough to handle it, it is the efficient way, and is working as designed.