Enemy poison and burn is far too strong, you should add ways to deal with it besides the one potion that purges debuffs and the rare stone that removes 1 stack per attack, it also feels like if you don't go cleavers or bow you can't win, which is a shame cuz this a unique game that I want to see grow. I think if you make the snakes poison an attack it would balance it out, plus it would make sense as snakes bite to inject venom.
You definitely can "win" (beat regular 9 floors) with more than just cleavers or bow. In fact thats what I was doing most of the time, and usually breakpoint was Magma Core+ (F16-18) for most of the setups. Yes you can get unlucky with either drops or the enemies / events, but thats how the game work.
Regarding poison and burn, I agree. Poison is simply cannot be survived after regular floors anymore, burn can be mitigated by block but on high values you also start having problems (like you cannot build more than 999 block for some reason and will die eventually).