I'm sure there are some general guidelines, but no hard rules, although there should be. I haven't put all the powers into formulas but I tend to go with the rule 'If everyone wants it, then it's broken'.
Some general concepts I tend to see with powers, most are obvious and I'm sure everyone sees the same. At-will powers deal 1d10 like most big weapons. Now they deal less and less when adding things, such as slow, mark, or can be used as basic atk. Utility powers do not deal damage, and they should not IMO. Dailies follow At-will powers generally. I'm thinking the fighter 1st level 3x+str damage followed by the less damage and more other things like push+2xdamage, 1xdamage and sustain minor, etc.
I guess you would need to try out new powers with the understanding among your players that you can lower the power of the power or raise the level after playing with the new power.