Most of us don't waste time in the DA.
First of all, the distinction should be made between DA-Furball lake, and DA-1v1s. Typically when someone calls out "DA", it implies One Versus One fights, same plane, same alt. And it is not a waste of time. The reason the Muppets are able to intercept your guys missions and be incredible pains in the arse consistently is because we have spent countless hours fighting 1v1s in the DA, honing our skills as fighters, and becoming incredibly confident at fighting in close quarters. Not only that, but it gives you a better intrinsic sense on creating angles, aiming timing, and just general uberness. Not many players want to spend the time and effort it takes to become really good and effective in the MA and I totally understand that, but calling it a waste of time is off base.
If you wanted to, you could basically look at the DA as practice for the game, which is the MA.