Under PF core rulebook page 197 it states that "Aid Another" is an attack roll against AC 10. Some of our first level characters have a +5 to hit. When level 5 is reached, a fighter could easily have +12 or so. A rogue, monk or ranger +10 with a feat or two and great stats. That would seem to indicate that to hit +10 is automatic (barring a natural 1). Was this the intention of the game? I'm going to assume that the idea is that a level 5 character should have something better to do than aid another. But would it not be beneficial in a situation where an enemy becomes fixated on a character and you have an opportunity to boost his AC by +2?
The Aid Another action gets a lot easier as you gain levels, to the point where it's nearly automatic for all characters at mid to high levels. This is probably for two reasons:
If my attack roll is already a +10, then adding another 2 isn't that big of a deal. However, at early levels, if my attack roll is only +3, adding an extra 2 is a big deal. Likewise with AC.