There is clearly some randomness in what happens, however peering throught the fog a few things stand out:
Campsites look like empty levels that don’t have much effect.
Gaining access to treasures looks crucial for having a good chance of defeating the boss, and you normally want at least 2.
Everyone always gets past level 2. The only cases of heros being stopped at level 3 are Mages by Jar Worms. For warriors/rogues cultists and Jaw Worms seem to be equivelant but Jaw Worms are Mage eaters.
Only Mages and Rogues get stopped at level 4. All rogues are stopped by slavers. these may be specialist Rogue killers like the Jaw Worms are Mage killers.
The first warrios to be stopped are at level 5 which are all stopped by sentries. Specialist warrior killers.
I put together an algo to estimate the chances of beating the boss which took account of the treasures that had been picked up and the chances of being stopped before reachingit which suggested the following:
Simple Tower: Send a Rogue along the following path: START ->Tome of Knowledge ->Jaw Worm ->Jaw Worm-> Dagger of Poison ->Cloak of Protection ->Chosen ->Shelled Parasite ->The Collector (Estimated win rate 90 percent)
Advanced Tower: Send a warrior along the following path: START ->Gremlin ->Jaw Worm ->Adamant Armor-> Enchanted Shield ->Sentries->CAMPFIRE ->Vanishing Powder ->The Champion (Estimated win rate 94 percent)
A number of other possibilities seem to be very close to these, so I am not that confident that they are optimal.
Thank you for posting this. I found it easier than most D and D scenarios, complexity 2, quality 3 (Assuming you are only trying to get a good answer, trying to unravel the algorithm behind it feels more like complexity 5).