What is the best level-select strategy for heroes?

We play with 3 heroes - Disciple Avric, Necromancer Leorik and dwarf (can't remember his name) berserk.

After winning first blood we have chosen Dareon Castle level, but lost the second phase. Frenzy+blood rage on red ettin left the guy we had to protect with 8 hp out of 25 after first OL move.

We are gathering for next game in a week. The next level will be The Fat Goblin.

So my question is - what is the best sequence of levels to choose from act 1/2 for heroes to win?