I've heard a lot about these opponents - Mom in particular - but was never pitted against any of them (initial Gary battle aside) when I was playing PvP. Now I'm tempted to set up a custom scenario or two to see if my standard party can take them on. 'MP AI Priest 1' etc. are presumably the enemies I'm looking for; does anybody know which combinations are used by each of the AIs?
Just doing some spectating in the MP room, it looks like it's random. For instance, one Gary fight had elf priest / dwarf warrior and wizard, but another had elf priest, human priest, elf wizard. Melvin had a 3-dwarf setup in one fight I saw him in.
Party 1 is Gary's, 3 is Melvin's, 5 is Amy's; you'll also see those in the Card Stock II Preview. Gary has at least one other party, not sure if it's 2 or 4 or unavailable; Mom's party isn't available in custom scenarios. I should experiment a bit on the test server.
After some testing, I see that Gary uses party 1 and 2, sometimes mixing chars from both. Party 4 is: Blessed Anrime (Elf Priest), Krelvin (Dwarf Warrior), and Mingolborn Pain-Bringer (Elf Wizard). It's possible these are extras for Amy and Melvin's MP parties.