I played this on hard, as a rogue. Cleared it at level 3 with a party of myself, fighter, wizard and priest. I stealthed, placed a fireball trap and then pulled them to the doorway where my group was waiting. On the way over they triggered the trap.
Now on hard, there were 2 shades and one shadow. The shades are level 10, and will summon a shadow. If you kill the summoned shadow they will summon another, but if you kill the shade the shadows go away. I took out the non-summoned shadow first, then focused down the shades. They are weak to fire. I used the increased defense and increased accuracy party buffs from the priest, along with the level 2 ground zone regeneration spell he has. Knocking them down doesn't seem to work, so don't bother but that wizard cone flame spell did wonders. My rogue didn't seem to have a lot of luck with his bow, but sneak attacks with his estoc sure seemed to work well.