Here's a look at the raidwide damage that goes out during the Kor'agh fight. While there are definitely additional challenges - moving away from suppression zone smashes, single target healing during Rune of Nullification (Phase 2) on the soaker and the add tank, and finally keeping the MT up as Kor'agh's stacks grow near the end of the Barrier portions (Phase 1) - this is a significant challenge to the raid team to manage through the raidwide damage that goes on.
I'm not sure there are any great weakauras for the timers on the Expel Magic casts out just yet due to the way the timers go on pause when the raid pushes him into Phase 2 and then pick up where they left off for Phase 1. I'll set about creating something usable.
Our team personally got much better at moving out of the avoidable stuff as progressions continued and our tanks got better at controlling the adds. Feels like we'll have this thing nailed very soon.