... against a foe with a high AC, careful strike will be better.
And note that you don't compare careful strike with the basic attack, but with the other at will power (same attack bonus and damage than the basic attack, but with a free shift before or after the attack), or any other at will power that your ranger would take at first level.
Before the errata, some players said that they almost always used caraful strike, and not the other at will power.
With the fix, I expect the choice to be more interesting ...
