Here is another opinion I have: if you are playing Synod, you should probably be playing some number of Thoughtcast. Synod is a greedy card and you should be rewarded for your efforts.

It doesn't hurt that Baral discounts Thoughtcast but does not discount Preordain.

I don't think that running 0 Preordain is ever correct, but you could run a split perhaps.

Edit - I'm not sold on Shoal like the OP is, but at least Thoughtcast recovers the lost CA while Preordain doesn't. But you still often need Preordain for t1 to get things going.

I prefer the more resilient versions for several reasons. Though I haven't been able to join as many Dailies this month as I was in May, June, and July, I had a lot of success then with lists that walked the line between Paradoxical control and Cantrip Gush-Delve.

The main reasons I've preferred the Paradox lists with a Mentor win-con that are not "Opal Soup" are:

Lower frequency of hideous mulligans. Less games auto-lost due to inactive Mox Opal(s). Better equipped to win despite Stony Silence/Null Rod. Monastery Mentor is the best answer to Monastery Mentor Able to change roles, particularly post sideboard. For instance, when an opponent can be expected to overboard v. Paradox with Null Rods and artifact hate, I board out Mana Vault, sometimes EE, and 1 or 2 Outcomes, morphing into more of a straight up Mentor deck. Paradoxical Mirrors. The control/resilient versions have been substantially more favorable in matches v. the combo lists.

I know people have had success with it, but I am very wary of Salvagers in Oath, since I expect 1 Oath activation to be my plan against shops and White Eldrazi, and Salvagers isn't usually.

Re:Ritual vs. PO
It's a complicated question and one that becomes more muddled as you add cards like the 1cmc tutors and 1cmc anti-hate to PO; since it opens you up to Mental Misstep a lot more, and as such nullifies one of the more strategic advantage of the deck. However, it's worth pointing out that Ritual-based Storm is significantly more hampered by Graveyard hate (specifically Tormod's or Leyline, though I suppose RiP also falls into this category) than PO. It relies on YawgWill and Dark Petition w/ Spell Mastery quite a bit. Given that graveyard hate will always be a thing in Vintage, and in rather large numbers - I don't feel that Ritual Storm actually manages to sneak in under the blanket of hate that PO faces.

Now, what are the advantages of it? Well no one is running maindeck Tormod's Crypt or Leyline. On the other hand, you also aren't as likely to just win the die roll and kill your opponent right then and there. In terms of the raw power, PO blows it out of the water.

@BandsWithOthers
I've been toying around with a few things. Mindbreaks in the side, Mindbreaks in the main. I quite like the Mindbreaks in general. Especially in the mirror where a single Force on the Draw is often just not enough to save you from the opponent doing silly degenerate things. I have yet to really settle on a sideboard configuration that I like, but I do enjoy how much room you actually have with this deck. Outside of the obligatory 4x Hurkyl's, 1x Blightsteel, and 2x Flusterstorm, the rest really feels quite transient. I think you likely want a total of 3-4 ways of removing troublesome hatepieces between the main and side as well. Currently I'm trying out Disenchants to bypass that prior mentioned Mental Misstep issue.

The one thing I am definitely sold on is the Torrential Gearhulk though. Card has been absolutely amazing. Between ease of hard-casting, pitching to Force, being able to get value even vs. Swords to Plowshares, and turning Tinker into a PO (after the first has been cast) - while actually being a pretty respectable body against the crap that White Eldrazi/Shops populate the board with, it has just been fantastic.

Yeah, that makes sense. Thanks for the info!