I installed Masque today to use it on WeakAuras. I applied Clean Icons - Square to my WeakAuras.
As you can see on the following picture it is working most of the time. But sometimes when new Auras (in this case - Buffs) appear masque is not applied to them. You can see that on the 14 seconds blue buff on the image.

Added support for dynamic groups in bb27b75.

This is something Weak Auras will have to address, as Masque doesn't monitor changes, etc.

Ok. I reported the issue here: WeakAuras/WeakAuras2#1111