For everyone with the XP bug there is a mod which fix the problem.

nexusmods.com/witcher3/mods/119/?

I can' t test it by myself because I don't have the bug, but let me know if it helps.
Thx to pcgameshardware for the hint.

I just use the dev console mod to give myself whatever xp I feel is right, 3 nekker hearts and 2 of those ultra rare vampire skins you need for potions.

I'm really tempted to use the console to give myself those vampire skins too, seems to you at least 3 to upgrade potions and oils. In 100 hours i've found one.

as this mod isn't actually a fix it's more of a work around that changes other parts of the game(it rewards XP for grey quests) i think it's a little bit unfair to claim this is a "hotfix witholding desaster" would you rather CDPR rushed out a fix that could cause more bugs & problems? i prefer it if they take a little extra time & make sure the bug is fixed & the patch tested

The official explaination is that the fix is done but since they dont feel the game balance endangered by the xp glitch, they withold the fix until they can ship it with the rest of 1.05

Instead they release a 0,9 MB Patch that does nothing but break third party software compatability. ;)