The Straywood utterly owns Domination. You want to get creatures out as fast as possible. Flyers rock. Fast rules. Put those together....Straywood owns Domination.
And since cheap creatures and Flyers are important, so too are zone attack spells and mass direct damage (like Idol of Pestilence, Altar of Skulls, Poison Gas Cloud, etc).
Elusive is also very important - hence Slaknir/Goblin swarm being pretty awesome, as are Cervere and Rajah and Tarraki. And the Druid restricting movement via Vine markers and Snatchers is pretty amazing. And the Necromancer's ability to swarm while simultaneously punishing living creatures (via Idol of Pestilence or Altar of Skulls) is pretty amazing. And the Siren's ability to prevent creatures from doing what they want (via Siren's Call or Love/Hate relationships) is pretty amazing. And Grapple and Trample look like they could have big impacts on Domination (although I haven't used them much yet). And despite all that, I pulled off a 3-way victory with the Priest a couple weeks ago... so you never know what might win in a given match.
Also, don't underestimate creatures that have passive abilities. Wychwood Faerie is borderline broken if ignored, since she provides a mana discount but can also tag orbs. In one Domination match, she hit 3 or 4 orbs for me while saving me 4 or 5 mana over the course of the game. Similarly, Disciple of Radiance is pretty amazing. She can pray to a temple while dealing direct damage to a Sslak/Usslak and/or your opponent's creature, or even passively deal direct damage to finish off a Sslak before tagging the orb it was defending. Compare to the Monk who has to spend his full action in order to channel an extra mana, or the Azurean Genie who has to waste his action to benefit a creature.