So, I think I'm missing a step in their logic. I understand their statement to mean:
- Mentor is powerful because it casts lots of spells and gains value from those spells
- Shops is the natural enemy because it limits spells
- Mentor is made more powerful by casting more free spells
- Shops counters with tax effects, which also limit the rest of the metagame
- Therefore, Removing (at least) 6 copies of free spells from Mentor decks will
(a) weaken Mentor decks
(b) reduce the inclination for Shops decks to play tax effects
My sticking point is 5b - why wouldn't Shops maintain an effectively same count for tax effects which will now be more powerful against Mentor (as they are replacing free spells with spells that cost mana) and continue to shut down the other decks in the metagame.
I'm unwilling to say it was a bad call, but I'm interested in diving into the thought process here because they actively stopped Shops from playing tax effects when they restricted golem to allow for more spells and the metagame has still become Policeman vs Spellslinger, so now weakening the Spellslinger should lead to the Policeman fewer tax effects than the effective ones the deck was using before and I find that counter-intuitive. It just sounds like they've set up the format to be wholly dominated by Shops again.
edit: I also wish that they let someone off the restricted list because I view it generally as a prisoner exchange system, but at the same time, I can respect the willingness to only make one change at a time.