I think the major issue regarding having an 18 or a 16 is the fact that you lack a lot of the buffing that were in 3.5, which means that your chance to hit is much lower. Not only that, you also deal more damage with a higher score. So you hit 5% more often and depending of your damage you may deal a rather high percentage extra hurt out. 5% more to hit means little with the at-will powers, if you miss you can just use it again, but encounter and daily powers are one-shotters. If they miss they are wasted.
In 3.X such one-shotters were either automatic hit or against a touch AC (and therefore a high chance of hitting). In 4e they are incorporated in all classes. You'll really hate yourself after missing with your daily power that could have turned the entire fight around.
In 3.X such one-shotters were either automatic hit or against a touch AC (and therefore a high chance of hitting). In 4e they are incorporated in all classes. You'll really hate yourself after missing with your daily power that could have turned the entire fight around.