Look at Sure Strike (fighter) and Careful Strike (ranger). The math seems to indicate that those powers are rarely if ever going to be used or if they are it’s because the math isn’t obvious. The +10% chance to hit is outweighed by the damage you give up with either Twin Strike or Reaping Strike/Cleave (situational).
I’m tempted to split the difference, the various math’s posted seem to indicate that +4 makes them numerically ‘right’ in that they don’t do overshadow the other powers but in specific situations they end up being valid choices to make and give them both a +3 just to see how that goes.
I won’t bother posting the links here, they’re all over the place and the math is pretty boring.
