My absolute best time is 12:27 with the Kronos exploding Mud Men strat.
The blessings are the Hades’ Watchful Wiles (Myth Unit HP), Hel’s Last Promise (Myth Units explode upon death), and Isis’ Divine Retinue (Myth Units cost less favor). You basically just spam mud men and attack right away.
My best time with a Norse God uses Loki with Kastor’s Elite Guard (starting units and pop cap), Gaia’s Lashing Roots (Hero AOE damage), and Kronos’ Drowsy Dance (slows units near Kastor). With these bonuses, you can cripple one of the enemies right away with Kastor micro targeting their laborers, before spamming Hersirs and taking out the other teams.
And my best Oranos time uses the same blessing as the Loki strategy, and just involves using Kastor and some Caladria to cripple Set at the start, and then advancing to making destroyer heroes and running over the other two enemies. I was a second slower with the Oranos strategy over the Loki strategy, haha. Some luck is involved in getting the AI to surrender, though. I think the Atlantean hero strategy is a little stronger than the Norse hero strategy, but the free myth units from Loki are a lot of fun.
Additionally getting a good relic early, like Kui Drum, Fur of Boyi, Grass Cutting Sword, Tyrfing, Angantyr’s Sword, or Eye of Horus can make the run a little better, too.
I imagine there are good times to be had using Halogi as a blessing, but I didn’t want to use him in the story mode missions, because he’s kind of overpowered, lol.
I know it’s not the most popular mode in AOM, but I enjoy it, and I know there are some better times out there. If anyone else is enjoying it, share your times and strategies 
I have won with Japanese, Chinese, and Aztec hero spam strategies, but they’re not quite as good as the Norse or Atlantean hero spam. I’ve made myth unit rushes work with Greek and Egyptian, but I can’t do it as fast as Kronos’ Mud Men. The hero spam strategy isn’t strong with Egyptian Priests in the few times I’ve tried it. I end up getting overrun. It’s probably possible if you’re able to reach a critical mass of them and get your trade route up, but I haven’t made it work yet.
I am hopeful that more 3 v 1 missions vs additional pantheons might be released in the future.
Thanks for reading.