I found a new addon released last week from Tekkub called idHitThat.
As can be seen in the picture below, it adds an icon in the bottom right corner of the character frame which appears when you press 'C'. If you click it it toggles through the different melee, ranged, spell, defense tables for targets three levels above you. Very useful! I'm hoping that a future version will write out what numerical rating is needed as well and not only percentages.