I tried to look at Art of Murded: Cards of Destiny (Steam version) and could not reproduce the main character's corruption even with 9069913d completely reverted. So it is not clear what exactly is going on with this game, but since the change here looks correct I hope it should be fine. FWIW Medieval II Total War loads DXT1 texture into a big DXT5 with offsets (offsets and sizes are aligned), decompression worked fine while compression had this issue.