Actually snake poison is cleaned on levelup and the poison is not cumulative which mean if you hit two snake in a row you will suffer 2 damage total and may avoid most of them by leveling up before. The muncher drop a single trap so if you hit 10x of them and trigger the trap later you get a total of 1 damage which is basically the same than hitting 10x blobs. The scrounger is indeed very annoying but it's a lvl 2 monster you need to compare it with turtle or goblin for example.
I think the real problem is the lack of a real easy mode so player have a place to learn how to deal with this impresive monsters without dying every 2 minutes. I'm currently working on this part.