Here are my votes, after playing through all 6 scenarios of "Season 0" OP at GenCon (as Vika) and looking at the character sheets of the ones I didn't play or adventure alongside:
Bard: Lem [CD] -- uses d12 for both divine and arcane spells, Lem is a great companion to almost any other character
Cleric: Kyra [CD] -- I really like the combination of d10 for her melee combat and divine spells, her "Fireflower" role looks fun
Fighter: Vika [CD] -- recharges weapons, and has d10+1 craft skills to serve as the team's go-to shipwright, I am looking forward to the RPG aspects of her "Blacksmith" role
Ranger: Agna [CD] -- recharges animal allies, interesting offhand weapon mechanic
Rogue: Merisiel [S&S] -- extra weapon to start, but I am torn between the massive damage possible with her "Shadow" role and the extra plunder and card swapping allowed by her "Smuggler" role.
Sorcerer: Seoni [RotR] -- recharges spells, quite the beast as she levels up
Wizard: Ezren [CD] -- "Transmogrifier" role looks like a lot of fun and very helpful to the team especially given that drawing a random "non-basic", "non-elite" substitute boon from the box means that at the end of the scenario, you are picking the good stuff out of your personal class deck in its place -- instant boon upgrades!
Of course, I also love Ranzak who is a lot of fun to play. Perhaps he could be played with a rogue class deck (he is however listed as a raider)?