It is really sad though that there are 7 classes that outperform Frost on it's niche fight (Jadefire, two targets close together). It doesn't help that the last couple of fights in BoD are basically a big FU to mages. And lastly anyone that played a mage in Legion will know how gutted this class is and how much of the fun has been 'pruned' away.
Being needed just because your raid needs AI, or decurses on Conclave is not conducive for fun. I guess that's why my old raid team went from 3 mages, to one that would rather play his Warlock, but can't because of the need for AI.
I didn't help either since I am on hiatus and levelling a Warlock myself to see how that plays. Having not played it in Legion I have the benefit of ignorance on what was pruned away from them, and due to that can enjoy its playstyle.
To be fair, being middle of the pack wouldn't be terrible if the gameplay was engaging and fun. Unfortunately we aren't really middle of the pack, especially not on fights that still matter, and Mage gameplay is clunky and unforgiving.
Better stack up on those Intellect Scrolls for the Eternal Palace raid