We Need Another MYMU
First off, while the original MYMU has generally worked well, a couple mages still could use some changes to their kit:

But second, a few mages could really use that level of change to their kits. Not a full-on rework, but they need some adjustments to their abilities:
all come to mind. Karma and Galio are relatively well-balanced but sort of bland. Aurelion Sol's skill floor is very high and his E has a lot of unused potential. Heimer has not really adapted well to the current meta and could use some changes. Azir has been problematic in the past and needs some changes so he's a healtheir champion.