Originally posted by SumatranRatMonkey:

It would help if mobs knew how to jump thin moats so it wasn't such a cheap tactic.

If a 2m moat could be jumped, players would make a 3m moat...or a 2m one with raised earth wall as the inside edge. It's very difficult to do this in a way that is not exploitable. And you vahe to consider how much you really want to keep people from doing it, if that's how they want to play.