If you feel that way, you may not have figured out all the secret patterns and ways of using logic to deduce monster locations. It's almost always possible to beat the dragon (but not necessarily to get the achievements) with no unsafe guessing (i.e. no guessing where you might die based on the result).
There are patterns that predict the locations of:
Gargoyles
Egg
Walls
8-slime and slime sorcerer
Necromancer
{6-monster}
Rat King
Combine them and you can slowly chip away at the dungeon without risking a loss.
It's especially useful to understand that the 8s have specific placement rules, and there are only two 9s and one 11. That means you can pretty quickly reach a point where you can say "These three tiles have 15, but none of them can be bigger than 7, so I can safely make this the first click of my 7-health turn."