Guild Wars 2

Classes are not balanced around class stacking yet it has been part of pvp since… well pvp launch. It does not work, it causes frustration, it causes toxic behavior – nothing good ever came from balancing classes around non-class stacking and having class stacking in pvp.

https://forum-en.gw2archive.eu/forum/game/pvp/The-curious-case-of-class-stacking