I bet I piss a few people off by saying this but.....
I did DC for several months too. Was liking it too. But I noticed the SAME thing as you are saying happening to me. So I went back to that other board where DC reigns supreme and NOTICED SOMETHING that slipped past me before: While SOME of the DC guys are solid, high-quality looking bodybuilders, the VAST MAJORITY of DC devotees are just big, huge lug looking guys. No definition what-so-ever. Even the main man, Dante, though huge, once wrote, and I quote as best I can remember, that "some kids at the gym seeing his huge arms asked him to flex for them. So he throws up a bicep shot and the kids still say 'ok, now flex.'" His arms are so smooth that even when he flexes them no one can hardly tell! And he's not covered with blubber either. The fat, I believe, is marbled IN his muscles, like Prime Beef, like this picture:
Picture of marbled prime beef image by thirdeye2 on Photobucket
Look at a bunch of guy's avatars on that site and you'll see lots of big giant 35%plus bodyfat guys ( who THINK they are 15%). It's great to be strong and weigh 300 pounds, but if you have to lose 100 pounds to see a little bicep definition, I'll pass! I can't speak with ultimate authority but I believe that the DC training and eating style adds a lot of intramuscular fat.
I went from 219 to 247 doing DC in about 6 months. I got stronger than ever and all my measurements were their biggest ever. But I missed getting good pumps, really blasting a bodypart, and looking like a bodybuilder (rather than just a hulk). So I started cutting and switched to my good old Draper-style workouts with a little FST-7 style pumping added in. I'm now back down to 215 and I look and FEEL way better. I'm not sure I gained any useful muscle mass from DC. Like I said, I think it might have been mostly intramuscular fat. When a DC guy calls himself "Prime Beef" he probably doesn't realize that "prime beef must contain no less than 8 percent INTRAMUSCULAR fat!"
DC is, in my opinion now, is just for becoming a bulk monster. Sorry DC guys.