User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-77.253.101.192-20141123093720/@comment-24468758-20141123162404

You can pull out the power of BG and DD better if you work together with Draig and Albion as Issei and Vali are both pulling out more power than any possessor before them. They themselfs can't access their own original power as shown with JD that released a huge part of their original power by force, the jewel of Issei's possibilities that had the pulse of Draig's original power and the most of their former abilities such as reflect and penetrate are sealed.

With the way JD works it's easy to see that they can only help the possessors as Draig wasn't able to stop Issei from activating JD as he would have done it if he was capable of it.