I'm at a loss to explain your results or direct you on what to do next. One would think that amount of DPC Latency would be devastating to any performance in game play. Yet you only encounter problems in StarCraft 2? No problems in other games or streaming YouTube HD videos?
One thing - if you turn off Vertical Sync, Antialiasing, and Ambient Occlusion, does it change the behavior in StarCraft 2 or DPC Latency Checker?
When you choose to re-install your NVIDEA driver, boot into Safe Mode, choose "Custom Install" and check the "Clean Install" checkbox. Hopefully, this will prevent other running drivers from interfering with your re-installation and remove any remnants of previous NVIDEA installations.
G74SX-A1 - stock hardware - BIOS 202 - 2nd Monitor VISIO VF551XVT