I'm not yet putting the Alchemist on the Warlock level, but I can see a lot of possibilities for him to get there. It's generally the power creep I'm worried about.
Base game has 1 character in a high tier: Troll (7-8 record)
Reaper, also 1 character: Sage (7-8)
Dungeon 2 characters, Gypsy (6-5) and Gladiator (5-6), with Amazon not far behind
Frostmarch 2 characters, Ogre Chieftain (5-4) and Warlock (5-4), with Necromancer bit further behind than the Amazon, but still better than all base + Reaper chars.
Of the base + Reaper chars, only Dark Cultist (5-10) and Elf (5-11) are close to upper mid-tier and even they lose two out of three appearances. Will Highland give us 4+ top-tier characters?

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