Matt, a quick question on exclusive access in the WDM context that may be relevant to OP's concerns*:
Back in the loopback days if a program tried to take exclusive access of the soundcard being used for the dummy in loopback, it would break loopback in MC (e.g. if I used my realtek on-board as the dummy loopback default device and targeted it for output using a program that took exclusive control of the device, attempts to open loopback would fail in MC).
Some folks are reporting that WASAPI exclusive output modes targeting the new WDM driver are causing playback to stutter or fail:
http://yabb.jriver.com/interact/index.php?topic=92593.msg638476#msg638476When I tested, I had mixed results myself (sometimes fine, sometimes not fine depending on the program).
Does the WDM driver work correctly on your end when using a program that takes exclusive access of the JRiver WDM device?
*Obviously allowing devices to take exclusive access of the WDM driver is a different issue than enabling exclusive access on an output in MC, but I wasn't sure which one OP was asking about.