What I need for d20 creature design:
A software program where you plug in the stats of a monster and it runs a few tests (expected damage per attack vs various character types and things of that sort) and tells you what the suggested CR is. I would be perfectly happy with it flagging things it couldn't factor in, but I wantsss it.
Also, why are there CR 1/2, CR 1/3, and CR 1/4 creatures, but no CR 2/3 or CR 3/4 creatures? It seems like the lack of resolution between CR 1/2 and CR 1 hurts low-level encounter writing.