Drgs are nothing to sneeze at. Their sustain is lower then Mnks, but they are still the king of bursts. They can burst like no tomorrow if you need them to. 3 GCD to max out damage mods is a dang fine thing.
They balancing each other decently. Sometimes mnks are good, sometimes drg are good, sometimes both aren't bad.
And mandatory positional aren't really...that mandatory. Heavy is a 1st step, and ID is a 1st step. The only 2 you need to be in position are both 1st step.
That means at most you loose a GCD worth of damage, and that's way way way better then loosing GL. that requires 9 steps.
If a drg isn't stingy about his timing, that means his buffs like BfB and IR are both well timed to be right in the middle of a no positional rotation, making the duration even more damaging.