Its a little weak for a Dunkelweizen, but that's not necesaryily a bad thing.
For my taste, you have too much chocolate in there, and having no crystal and using sugar will make it too thin. DW's should be dry, but not thin. I'd throw in some dark crystal. I like 4-6oz each of C40 and Special B in mine.
This is a beer that shouldn't have any 'roast' character, imho. 8oz of chocolate will start to get roasty, especially with no crystal to cut it.