If I could post images on here I would but I can't. I guarantee, though, that they would not help you. And I'm sorry but I just don't feel comfortable posting a dxdiag publicly.
I posted this thread in the hopes that either: a) Bethesda would be willing to give this issue some attention, or

Someone else who had the same issue would have a solution.
All my drivers are up to date, yada, yada. I've been building computers since 1992, I'm not new to this rodeo. It's not impossible that it's a driver issue, but the more specific the problem is -- and this one is very specific (only Skyrim at 2560x1440 in first person view) -- means that the problem is related to that specific scenario. Which makes it more likely in my mind the bug is in Skyrim's code, in the way Skyrim is handling high resolution first person view. But of course we don't know. We're only guessing. Which is why I'd like to get a Bethesda dev to actually look into this.