Here is my -DT build:
Atlas+2/Eisen/____/Whatever
Versa+1/Twilight/Merman's/Brutal
Versa+1/Heavy/Dark/Dark (11% PDT/10% MDT)
Metallon/Turul's_thing/DS+1/Askar
52% PDT (caps at 50%, but you need to go over to hit the real cap)
22% MDT (need 1% more, better Dark ring I guess).
The sacrifices we make for 50% PDT allow other more durable jobs (like Monk, Ninja, or SAM outside Abyssea) to catch up to us. If WAR/SAM isn't using Hasso and Retaliation with a full Haste set, they aren't to be the best DD in the game. So situations that require durability bring our damage back in line (and possibly way below the line) with other DDs that start out more durable.