If the goal is to reduce misses, I don't really understand why it would be better to add a +2 to profiency rather than a +2 on everything for everyone (normal difficulty).
The balance between classes would remains the original one and we'll miss less often...
I don't think the goal is supposed to be just to "reduce misses" as much as to increase the impact of specialization on the reliability of your actions.
After all, from what I've heard the relatively light impact of proficiencies on the expertise of characters is a common complaint about the 5th edition.
Several weeks ago there was a thread about a bunch fo tweets Josh sawyer made on this very topic.
