Skipping some skills works great. I now got rock guy at level 17 and poison guy at 20. And I have totally skipped stone wall and poison cloud. They aren't even offered that often so I have usually some choice.
I think I chose wrong skill to skip for rock guy. My area meteor thing for rock guy is pretty nice now. It hits 17 squares and does 390-750 damage. Problem is that it is kind of pointless to have both that one and underground spikes. So I think next time I will skip meteor and concentrate on spikes that hit all enemies instead of just 17 squares.
