My download also is stuck at 92% but claims to still be downloading.
ok. mine got near the end, and failed, saying the gog server returned an unknown error.
i did a varyify\retry option, and it resumed, but soon the speed went to min, so i pused it and shut down gog galexy, then resterted and resumed, where it bumped up one %, and went till it got to 92%, at 70\70 gigs.......i left it for a little while (hell, i fired up the xbox), and some time later (30mins to 2 hrs?) it said it was installed. i think i might have pause\restarted galaxy a 2nd time in there somewhere, around 92%, dont remember.
it is now installed, and has 2 exe files, for xcom 2, and xcom 2 wotc. i loaded both up and played part of the 1st level to test and worked so far.
so apperntly they glicthed up with the math somewhere, either galexy, or its adding up the game size wrong...i did see that it started at 68 gigs, for a few moments when first starting it and it was checking the files...but then went to 70gb.
(apperntly tho wotc just adds new enimes\allys\systems to the game rather then a new story? i wasnt aware of that lol)
if you cant get it running, i did see that there is a way to configure your installation, so maybe you can try just doing xcom 2 base first, then adding in wotc, then the rest of the dlc.......at least you wont have to deal with all 70gigs at once that way so if it dosnt work, it wont take as long to find out.
anyway, hope this helps.
edit: i forget i also disabled vast antivirus. (left windows defender running)
re-edit: that should say "avast" antivirus, ops.