TrinityCore/TrinityCore — comment on commit bb0634c7c2f38409205db8b9c8b89f2bb6f54fb9
File:  line 0
By tobmaps:

Agree, not all auras should stack, but it should be handled like "disable effect of weak aura at more powerful aura apply and enable when powerful fades", it shouldn't be there. But for now i can only recommend you to use this workaround https://gist.github.com/1279062 (didn't tested yet, but should work)