I kinda speculated this, but I’m unable to replicate the problem outside of a specific driver in a niche situation on my 6700 XT. After switching back to the driver I was using, everything was fine. I’ve since upgraded to a 7900 XT, and still don’t have any issues.
If it was a power thing, you could increase your minimum clocks or/and increase your power limit. However, I ran both cards at stock with no issues (I did run my 6700 XT on an undervolt for a while, but those never seem to play nice with WoW, specifically). I tab in and out a lot, and WoW’s FPS minimum is 20, and max is manually set to 240.