Your problem won't exactly be solved by reinstalling the game
Your problem is that you have a model called HeroDemonHunter lying somewhere around in your Warcraft 3 folder which is buggering everything up, or a folder called "Textures" with a "HeroDemonHunter" or "Illidan" skin it which is corrupting things
Failing that, a skin which the two use which you have in your Warcraft3 folder which is corrupted or somesuch
Find that model/skin and delete/rename it to fix things
I THINK that could be the problem, seeing as I had the exact same problem in the past and that's how I solved it
If you play a normal Warcraft 3 map and the Illidan/Demon Hunter model appears, then this'll prove my theory correct