Depends on your intuition. For me, everything seems intuitive and normal for a D20 based game.
This. People generally have pretty bad intuition for probabilities. I'm an academic probabilist, and at university open days and the like we often play statistics games that capitalize on people's inability to intuitively understand random systems. It's quite rare to find someone who has a good intuition for randomness, which takes a lot of exposure to develop.
Game's randomisation seems fine to me.
