Thank you so much for this info, I can't believe I didn't see this in all of my research. With the information from that document I take it back. I am getting full bandwidth since 12 machines get backed up at a time. The individual VM transfer speed in the backup reports was a bit misleading to me since I didn't realize that 12 are uploaded to storage at a time.
My initial finding still stands though, going http completely removed the one bottleneck that we had in our backup infrastructure and made it 3.5 times faster then before.