Well, maybe not the dumbest thing I've ever heard...
I do think that most of the Duncan pickups are more complex in their tone.
However, for styles like metal, complex tones CAN make your tone mushy, depending on how you have the rest of your rig set up. In short, different pickups for different people. If your DiMarzio sounds good to you, fine. If it doesn't, try another DiMarzio. If you don't find one of those you like, try some other company. It's all a crapshoot depending on your style and setup, the strength of your hands, and technique anyway (and how your brain interprets sound frequencies, but let's not digress).
Bottom line: If you hate your pup, rip it out and try some more; that's half the fun anyways!!
Good luck!
Farkus