Given that 2.5 is in release and hopefully ED is done tweaking mag var factors, (and in my efforts to create an IFG), I've revisited the magnetic variation sim deltas relevant to the public mission (2011 mission year).
A couple notes:
1. Ignoring the magvar for a moment: The DCS Nevada map appears to be consistently off by a degree for TRUE headings from real world. This is possibly due to the flatness of the map, but whatever the reason, it's off by a degree. To demo this, compare the headings between two points on Google Earth, and the same two points in the ME. You'll note about a one degree delta. Nothing to do about with this, but it's worth noting for the following reason: If you look at the in game magvar for 2011 (e.g. 12.4 at Nellis), and try to deduct that from a reference point in Google Earth, you'll consistently be off by a degree. So simply note that if checking true headings in Google Earth, subtract one degree (i.e. if it's true heading 007 in Google Earth, it's true heading 006 in the sim.)
2. The magnetic variation in Nevada increases as you move North West. For reference, at the extremes of the map, (South East corner) the 2011 magvar is 10.6. At the North West, it's 14.4.
3. Ignoring the extremes, here are a few more relevant magnetic variations for illustration purposes (2011): Nellis 12.4, DREAM 12.5, Mud Lake 13.2, PINE 12.4, FLUSH 12.8, TTR 13.1.
This affects the accuracy of the FLIP, the Area Points Radial/DME data within the NTTR section of the site, and any procedures you might be using with radials defined.
Honestly, the FLIP doesn't appear to need much updating. I looked at the Nellis departures and approaches in the latest version, and except for Nellis runway (e.g. Nellis runway 3 is actually magnetically 027.6, or 028, the FLIP shows 029). I didn't check non-Nellis charts, points, and headings because... why. (*maybe* TTR plates/charts are interesting to update, but meh).
However, the departure/recovery Area Points are off 1-2+ degrees in some spots, and those deltas are substantial for radial based nav. They're also inconsistent with the FLIP.
Stuka -
I'm already working to get the correct radials for the primary nav points; I'm happy to pass that along once I've run through it if you're interested.