They need to revert the increased Arcane Blast mana cost.
It's ridiculous because it only unfairly effects people who used the intended barrage-terminating rotation, they shouldn't be punished for the Scorch exploiters.
Want my honest opinion on what I've noticed during that time frame I noted as to why it is how it is? The Mage class was veerrrryyyy potent at the mid-to-end times of Cataclysm, that many people thought, "OMG I HAS TO PLAY DIS CLASS I CAN HAS SUPER RAID SPOT AND GLADIATOR TITLE CAUSE I CAN PRESS BUTTOHN!!!". These people got into the beta and just loooovved how broken we were on beta (we were, I played on beta and could go days without dying to players or mobs). Then this went live and the above players all of a sudden became experts on both class design and maths. Now that we're being brought in line which is ultimately better for us in the long run..."ZOMG BLIZZARD IS STUPID LOLZ I CAN HAS DESIGN DIS BETTER LOOK AT MAH IDEAS BLIZZARD IS TEH DUMB".
Of course, they're more eloquent than that, but it's my honest to God moderator impression.
But you're relating it back to something that everyone of your selected "side" is doing. That is, relating it back to damage/brokeness/etc. I've mained a mage since late TBC, the QoL has never been worse then this. How can you honestly slander us so harshly and then look at the L90 talents? Every other class in this entire game (with the one exception of DoC for druids) is either a passive, a dps cooldown, or a very easy to use ability. We don't have that luxury for any of them. Not only that, we are the only class whose playstyle is literally situated around their talents. Your choice in the L75 and L90 talents doesn't change your playstyle, it determines it. This make the class homogeneous beyond belief. Go see for yourself. go to the talent calculator and look under "spec" for magi. We have about 6-7 things. With every other class, you have to scroll.
Our issues are currently masked by our decently strong damage output, which is sad. The specs need much more differentiation, the talents need to be reworked (mainly with the last tier of talents being decoupled from mana for frost and fire), etc.