I have been tinkering with the Frosthaven characters on Tabletop Simulator with a buddy of mine for a few quests. We just started a new one after completing the first one we tried with the Banner Spear and Necromancer.
On our second run we are using the Drifter and the Shadowstalker.
It's hard. Harder that Gloomhaven and the characters come with a much higher complexity that that of Gloomhaven. I love it and look forward to playing the actual game for sure. On the other hand, I would not recommend this game if someone were trying to decide between Gloomhaven and Frosthaven. We are certainly tinkering in the beginning stages but having completed Gloomhaven I thought this one would be easy to jump into and Isaac has certainly presented some significant challenges to look forward too!