Can we try to disagree without mean-spirited snarky personal attacks?
I'm at a place where I'm actually trying to understand why restricting Gush and Probe didn't changes things. And that isn't just a matter of berating other people, it's a matter of trying to understand how all the pieces on the board interconnect.
One argument is that Gush and Probe weren't less essential to Mentor than they were to other decks that really needed them in order to be competitive. Another argument is that Mentor is the real problem because it is the nearly perfect condensed threat in a format with 0-cost mana rocks and 1-mana cantrips. Another argument is that MTGO doesn't properly reflect the community as a whole and that it also facilitates a herd mentality about what deck to play.
All of these could be a factor, or even none of them could. It's actually a genuine intellectual, psychological, statistically, mathematical challenge.
At this stage, the thing I am most annoyed about is the angry oversimplifications and personal insults. I've started making an effort to make sure I am not contributing to that atmosphere.
But back to some of the substance of the matter:
If reduced variance is king, then one thing I will point out is that there are different ways of reducing variance and 4-5 decks in particular make me think of these ways.
Reduce variance by having fewer unique cards. If Shops has a ton of 4-ofs, and even some 5-ofs (Moxen), variance is reduced dramatically even though some people may not recognize it as such. Eldrazi decks function in a similar way.
Reduce variance by cantrips that dig into/filter your deck. This one is more obvious and represents the Turbo Xerox ethos: Brainstorm, Ponder, Preordain, Dack, Ancestral, Cruise, Dig, etc. This can be Mentor, but is also Oath. This category is massively overpopulated with card choices because of Wizards' design mistakes.
Reduce variance using a unique card or engine that creates massive card advantage, but faces strong hate. This is Dredge and Paradoxical Outcome. Bazaar creates massive card advantage in a consistent manner with the help of the Dredge mechanic and Serum Power. PO creates massive card advantage through zero cost artifacts aided by a little bit of digging (Thirst for Knowledge, Brainstorm, Ancestral). One is hurt by graveyard hate, the other by Null Rod effects and tax effects.
I will continue to argue that we shouldn't be looking to restrict any more cards (except maybe Mentor). What we need instead is new cards that counteract the two dominant strategies. Shops is easy to fix--just create a spell that kills artifacts in spite of tax effects. I've said cycling in the past, but someone pointed out to me today that Channel is a keyword ability that exists and would accomplish the same thing without drawing a card.
Cantrips are also combatible: unrestrict Chalice. 1) Creature decks have Cavern of souls, and 2) Chalice helps prevent the format from being all about 1-mana spells. That may not be enough, but it would be worth unrestricting and then assessing.
As of today (and my opinion could change tomorrow), I think that Mentor is a genuine problem. And if Lodestone can be restricted, Mentor sure as hell can. Every time Wizards restricts a blue spell, it hurts most blue-heavy decks (Storm variants, Oath variants, Doomsday, etc.). Mentor remains the best "condensed" threat for the cantrip-driven decks.
While I recognize the raw power of Gush, in a format with Paradoxical Outcome and many tax effects, I don't know how truly overpowered it is. I actually like the Probe restriction more because free information that doesn't costs mana or a card, just life, hurts the play experience.
That's how I feel today, anyway. Some of it will probably change tomorrow.