I'd love to be in the levelling parties you're in where everything's dead in 8 GCDs - those sound wonderful, honestly. And DRK has practically no AoE MP gains until it gets its combo action, which is why Flood doesn't hold up to the others when they have combos. Blood Weapon will never give you a full Flood because of its duration (unless you specifically switch to ST for the 5 GCDs and drag out a pull, which the DPS loss is not worth), and Delirium is good for a burst of it but isn't enough to sustain anything.