I've had it for ages, just never been bothered to fix it since getting a new gw.dat didn't solve the problem.. Only just realized that nobody else I play with seems to have dead asuras standing about.
I'd be more prone to thinking it was a new bug if everyone had the same problem, but since it's only a few it's more likely a corrupt file.
Edit: After deleting gw.dat
again and downloading it one more time it appears that my problem is solved.
Unfortunately I didn't have time to check an already existing corpse (like the ones in Alcazia Tangle during the quest "A Little Help") but atleast Vekk is now on his back when he dies. His animations while casting also seem to be displayed properly. *yay*

Why it didn't solve it the first time is beyond me, but it appears it was a corrupt gw.dat