Initial reaction to any CXPacket problem on a global scale is that it's not the CXPacket's fault. Something is delaying one of the parallelism threads and that's the real culprit. However, I do recommend upping the baseline cost to 10-15 on any server by default, but that's simply my preference.
You've got a ton of scheduler yields but they're all short. I wouldn't sweat those. Backupthread can take forever, no biggie.
Async is off the charts. Your app or network appears to jam up on occassion. More information on that one: http://blog.sqlauthority.com/2011/02/11/sql-server-async_io_completion-wait-type-day-11-of-28/
After that you don't have any particularly significant waits.
So, I wouldn't tackle this directly from the Server. What else runs on this box? IIS? Reporting Services? SSIS?
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