1. Dany. Draw wins games. Throw in a great passive ability and lots of in-faction support and she's the winner imo. Immune to Tears of Lys, and if Targ retains their attachment speciality she'll be the best at staying unMilked.
2. Robert. Huge challenge str, renown, and character control in one package. Has Cressen in-faction for Milk.
3. Queen of Thorns. Economy is going to be a problem, at least early game, so her ability does a lot of work and allows a lot of tricks.
4. Tywin. Another economy helper and general large body for challenges.
5. Euron. The intrigue icon is welcome in Greyjoy but his ability is a little too situational.
6. Eddard. Decent, but stealth and other things can Throw an Axe in the gears.
7. Red Viper. Another hefty tricon, but his ability seems too hard to trigger for the cost.
8. Old Bear. Practically blank without the Wall in play. Putting a card into play at the end of challenges removes a lot of the potential Olenna has, and has a far more difficult trigger.