I have been playing the DV for several years now. I play a 10. I agree that the reeds can make a big difference as to how these sound. I think it's because of the "secondary window", which allows more of the reed to vibrate, thus emphasizing the characteristics of the reed itself.
I am using Vandoren Java 3's on mine and I really like them. I was using V16 3's but I found they could get a bit harsh sounding sometimes in the upper register. The Java's are a little bit softer and make the lower register more responsive and the upper register is amazing. I think the key to playing high on softer reeds is to make sure to keep a relaxed embouchure and don't squeeze on the reed.
If you want to hear how that setup sounds, you can check out my website at:
Go to the music page and listen to the first clip "funk demo". The solo is me on my Mark VI with the JJDV and Java 3's.