Yes, chocolate is fabulous as a high-end gourmet food, but difficult to replicate as a flavor element in
eliquids.
Double Chocolate flavoring concentrate from Capellas' line of Flavor Drops is pretty good for DIY juices. Not perfect, but close enough for horseshoes. Sufficiently rich to be satisfying, and none of that powdery artificial choco-cocoa flavor you've been encountering.
The chocolate flavorings from Lorann's and Perfumer's Apprentice are OK, but they don't quite measure up for my palate.
I recently bought some
Organic Chocolate Cake juice from VirginVapor with high hopes, but it was a bit odd right out of the mail. I'm letting it steep for a couple weeks (recommended for many VV juices---the flavorings and bases VV uses are so pure that they're a bit slow to develop full flavor after blending). We'll see how it melds and matures.