Answered your PM. But to post it here aswell. Why don't you make a huge slice texture with cropped slices? You can do any shape with the alpha channel.
http://www.wowinterface.com/download...07-Disco2.html
https://github.com/zorker/rothui/blo...banimation.zip
Optimally you have the animation as a video. All you need is Video to Gif and you are set.
Or you do sth way simpler yet super cool. You pick one of the amazing DisplayIDs
http://imgur.com/a/34ce7 (examples from the last 20k displayids, there are 50k more) and make your healthbar a rectangle scrollframe with a flat background and an animation on top. All you need to do now is chance the with of the scrollChild once the health updates.
That is what I am planning to do for my unitframes. It will look awesome because animations are super fluid.
Careful though. I tried adding 100 models to screen. Makes WoW go BOOOM BOOOM.