I have seen heavy maxdop interfere with writes and I/O, but it would have to be an extreme case for me to look towards that as a culprit. If you are going to adjust for maxdop, which I do on massive inserts mostly to save threads for other processes, I wouldn't go down to 1 initially except for simple testing. If you're getting 16 threads, try halving it to 8, and another run at 4. If you get nearly the exact same timing runs, leave it there as it's not helping you but will interfere with other pieces of the system.

+1 for Grant's observation about the CPU monitoring in VMWare as well. It's a skewed lens to look at the system through unless you're in the VM software itself.