Originally Posted by
Tekc
I can confirm this.
Did mythic + on the beta in both specs.
Disc is doable, but requires a bit more synergy between you and the tank, you don't really have an "Oh-shit" heal for him, so the damage has to be somewhat consistent.
Holy has a couple of good spells for those kind of situations, and is also slightly better on the move.
In the end I'd say, holy is safer because it gets the job done, and there is a higher chance of you recovering if something goes wrong.
Disc is best if you can make the group dance for you, it brings damage, the dungeons will end quicker, and you'll get more loot.