Isn't this going to be all but irrelevant in raids? You just need to get some Tomes to change your skills up. I don't know how Mythic+ works but it seems like no real problem. Worst case scenario, you can just swap to Aff or Demo depending on the encounter.
Like, if we can do good AOE, good cleave, and good ST depending on our spec, we're completely set for progression. That's the system working as Blizzard indended.