I guess it would be easier to try and buy BTC with the CC and then buy DRK, the problem with the credit card is because of the charge-back issue I don't know of any service that offers that.

EDIT: I did use Virwox once, but there was a daily limit of 100USD at the beginning with the credit card and a lot of fees, so it was too little for me.  Ever since I just do private deals to acquire BTC from people and buy my DRK.