The Wizard/Tower errata is the best thing to happen in MW in years. I completely support the errata, and the game has become sooo much better since. I say this as someone that exclusively played Wizard in tournament games, but it's made the casual games much better too.
Wizard was definitely overpowered. It was the top tier all by itself, with nothing on a par. The top few book archetypes were all wizards. Moreover, time and time again you would see people post book concepts that were perfectly in theme for the mage they had chosen, and often the experienced players here (myself absolutely included) would point out that the if you swapped the mage for a Wizard the book got better, 98% of your card choices still worked, and you now had an extra 10-20 spell points to play with.
I have played around with errata ideas on both cards myself, and dozens were suggested here. The problem was Wizard could take any of them, even a lot of them combined and still dominate. To be honest Wizard could have lost all elemental schools and been fine, but it was critical that it lost Water and Fire, and it's for the best that it lost Earth too. The Tower errata is honestly better than anything I came up with, and it's perfect.
At a very casual level it wasn't needed (and anything beyond the broadest balancing isn't) but even at the more experienced/serious casual play Wizard was a problem, and competitively it distorted the whole game. It was killing Adramelech Warlock, it was hurting Arraxian and both Warlords, and the new Siren was never viable as it stood. It closed off so much design space for the future too...