You could, if you wanted to, download and try the save, just don't talk to vulgrim right away. You can equip the horn and continue on through the game, avoiding vulgrim until after you kill the bat queen.
although the current save is on normal, the apocalyptic one is in progress..
[Superedit] I have been playtesting this new save, and I have destroyed Tiamat just now. Vulgrim is not completely broken, only the shop is. The serpent holes seem to work fine. I am going to create a new save starting at the crossroads for each difficulty level with all of the enhancements, level 2 sword and level 2 harvester, and everything you can purchase from vulgrim up to that point. I am going through the game on apocalyptic and I am cutting through everything like a hot knife through butter. I am sure I will find a point where vulgrims shop may be accessible again, when I do, I will update with a new thread and all 3 saves, each with a readme file explaining when you can talk to vulgrim.