I finished with knight-druid-sorcerer-cleric combo leveled up to 15. The point of keeping your level low is to finish the game in less time (training takes weeks at higher level).
With a druid you can get grand-master alchemy, which allows you to brew black stat potions so that you can get skill points from challenges. You need those skillpoints if you plan to keep your level low.
You need to max out bodybuilding on the knight to serve as a pool of hitpoints for the party to be accessed through a "shared life" and "regeneration" combo. You could probably do this with a monk too, but you would need more levels to get enough hitpoints.
Your cleric needs grandmaster body magic to prevent eradication via "protection from magic".
Your sorcerer needs grandmaster water and air to get invisibility, flying, town portal, and lloyds. Also, grandmaster water gives you a nice damage dealer in the form of poison spray if you go light (dark gets shrapmetal, which is better). If I recall correctly all horseshoes went to the sorcerer.
This was all quite some time ago, so I don't remember how frustrating it was to clear the lincon with that group. It was definitely possible though. I ran away a lot.