Here's my updated build:
This is probably about as good as you're going to be able to make it without adding power. That said, this deck is very, very weak in the current Vintage metagame.
First of all, by not running any Moxes, you can never cast a first-turn Oath, which is a
HUGE play for Oath. Secondly, by not running Time Walk, you are giving away many wins that you could have sealed. Time Walk is critical in Oath, and often means an instant-win.
Those two shortcomings severely cripple this deck.
Another aspect I wanted to comment on was the Muddle the Mixtures. I played an Oath deck with Muddles in it for a long time. They worked very well, since Transmuting can't be countered (only Stifled), and my deck had several decent Muddle targets (Oath, Echoing Truth, Time Walk, Demonic Tutor, Mana Drain, Regrowth). In my opinion, the strongest synergy was with Time Walk and Regrowth. If I resolved Oath, I could Time Walk and get a free hit in. Then I could Transmute Muddle for Regrowth, Regrow the Time Walk, and Walk again for a devestating second consecutive turn of Oathing and attacking. Without Time Walk (and Regrowth), Muddle is considerably weakened.
Also, I often found it was merely an overpriced tutor, and made the deck too slow. And I only ran 2, and I had good tutoring targets. You're running 4, and you lack Time Walk and Regrowth. That's waaay too many.
I understand why you're running Compulsive Research over Thirst (because you have no artifacts), but I think you're underestimating the efficiency difference between an Instant and a Sorcery. In the early game, if you have 3 mana available, you can keep it open to represent Drain, and if your opponent passes the turn without doing anything threatening, you can spend that mana on a Thirst to dig 3 deeper through your deck. With Compulsive Research, however, you have to tap out on your own turn, and basically give your opponent a turn to do whatever they want.
In Vintage, if a deck doesn't run power, then it must punish the decks that do. That's why Fish runs Null Rod and/or Chalice of the Void. Your deck would seriously benefit from either of these additions. It would at least buy you a little time, which you'll dearly need to cast those slow sorceries.
My recommendation to you is play in proxy tournaments and add the power to this deck. Even
with power, Oath is a tier-2 deck these days. Without power, it doesn't stand a chance. If you can't find any proxy tournaments in your area, I would suggest you put together a Fish deck packing Null Rods.
