What's wrong with all thieves having covert, isolate and climb? No one in their sane mind will spend points on most of those skills. If you're afraid of OP 42 thieves, unlock the skills at 47-51. I think it won't be disputed that thieves at 51 are worse off (competitively) than any other class. This would allow for a range of tactics that's currently remains unexplored. If you're too worried about cheap shot, keep it pointed, but the vast number of these skills are very niche and don't really add a lot to the power, just to the possibility of tactical uses of some of them in some situations, which will make the class more interesting. There's nothing OP in thieves, especially now that devious is unattainable for 99% of them and two devious is simply impossible.