I am not sure of the behavior. The last thing I remember as stacking and showing it was with bloodboil. We are not on yogg yet so I cannot actually debug your specific case. If you look at the code and search for stackable you can see what other fights ought to show stacks...
Vapors on General definitely show stacked on Center Icon, will try a corner text spot tomorrow, appreciate the add-on quite a bit (beats adding everything by hand by far).
It is marked as stackable. Iit ought to show stacks. What indicator do you have it hooked up to?
Tried center icon and CenterText3 for sure, maybe a few others (killed myself about 10 times with various combinations). Will be more thorough next time I'm down there if it looks like it should be showing. If I tie it to a text spot, should it have the stack count or just the name of the aura?