PX deq credit: send blkd

I am running a create unique index command on a table. The table has about 300mil rows and has a DOP set to 8. The index took about an hour and a half to build (also 8 ways). During the build I have noticed a jump in waits for PX deq credit: send blkd. I'd like to see if I can do something to reduce these waits and hopefully to reduce the time it takes to create the index. I found a few articles, but they all concentrate on issues with a nonparallelized select being feed by a parallelize insert.