Has anyone used candy melts to cover Oreos? If so, how many could you cover with a 12oz bag of candy melts? When I did it I could only cover SIX!!! Is that normal??

I'd say no.  I'm guessing you're using Wilton's.  Their melts are thick, especially the white and colored.  You could try adding a bit of crisco to thin it out, and you should get more oreos covered with the thinner chocolate.

AI've done that, I had to keep reheating the melts to keep them runny enough. I did quite a few, I know I got more than 6 from a bag.

Just did a cake pop class last night. She used Merken's candy melts and paramount crystals to make the candy coating thin. She made it look so easy...lol

6 is not normal, nor is 8. I think you can get at least 12 from a bag. The chocolate must be runny, which Wilton candy melts is not. It is thick and hard to work with. If you add shortening, It will help but not much. And if you keep reheating you are probably overheating it which will thicken it.Add Paramount crystals to thin it out. Better yet, use a better quality melt such as Merkins. I never have a problem with that.