Ok Evilsod, I did notice a few things. Also, it might be easier at your stage of mapping to post the zoomed-out view...sometimes comparing those rapidly back and forth lets you clearly see a corner or edge piece that's missing.
From looking at the full-res that you posted, here's a list of things to check:
1) The Ice Tooth Cave area, northern edge. Appears to be somewhat cloudier than what I've got.
2) Talus Chute north edge I THINK is foggier on yours than mine in places, but it might be an artifact of your collaged image. Still worth looking at closely in-game.
3) Far NE corner of Whitman's Folly seems to have a bit of ghosting in the blacker areas.
4) Far Easter edge (roughly middle of the zone) of the Marhans Grotto explorable area. Part of the "coastline" is what caught my eye
5) My Frozen Forest northern edge looks more solid than yours, but again it could be an image artifact. I'd check it on your map to be sure.
6) In Tasca's Demise, I notice a dot in the far north-middle.
7) In Mineral Springs, roughly middle of the northern edge there is this icy lake area thing (aqua in color on the map). I see more revealed on mine to the north of that than on yours.
8) Check your Iron Mines East and West edges. They both are missing parts at roughly the same horizontal position, around where the first icy lake is
9) Lastly, i hate to say it but....you need to do Thunderhead again lol. The black area on the north-western part of the map is missing some.
That's all I could glean from what you posted, but please give an update on your percentage after you hit all those