To finish that lvl you must kill alchemist. The strategy (long but effective) I chose was to take a brawler, pick up the heart and beat alchemist in the most upper part of the room. Healer and mage monks were taken to the lowest part of the room so wizard and alchemist won't see them and thus won't hurt them (They are easily killed by 5 wizard strikes, and healer monk are really weak in healing and have a little mana). That took long time really, but at the end, i beat alchemist while all of monks stayed alive. After that there are 2 more levels to finish the game. I did the same on both of them and finished the game!
The only problem of this game (a bug maybe) was that I never saved the game. Autosave were enough. But when you finish it once it asks you if you want to play it once more but on a harder level. I chose yes and closed the game as soon as it started (I didn't have enough time to play it more). But on another day I started the game and the harder level didn't load. Autosave was broken... So that was it. I didn't want to start it from the very begining to achieve the harder mode once more. Who knnows, maybe the same problem is in Driftmoon.
Anyway I had fun. Thank you for MB2!