The problem WoW faces is it has two fronts that it fights separately with the same resources. To balance in PVP it messes with PVE. To balance PVE it messes with PVP. If Blizzard would make these two separate fronts, each with its own resources, instead of one single front in which numbers and mechanics work whats best for each than you could strike balance. Until that point you just have a tugging match between one side screaming imbalance and crying about nerfs and back and forth. It is a pretty solid tradition in WoW and pretty much always has been since around BC (since in vanilla they didn't give any shits about PVP balance).
A great way to do it is resilience. Any target that has resilience (all players do as a base now) it effects spells differently. Causing different effects. At the core spells can be relatively the same in design. But things that prove to be needed in PVE but OP in PVP can be worked differently to prevent it. Or, even without the resilience thing, Blizzard could just DO it. Like they already do with some spells. But for some reason it burns at their core to do such a thing.
So imbalance is here to stay.