If you're not sure what hit rating is, I'll explain. When attacking a monster, with spells or physical weapons, you have a certain percent chance to miss them entirely. This chance is based on the type of weapons you're using and your level compared to the level of the monster you're trying to hit. So for max levels attempting to tackle boss content, there's a certain amount of +hit gear that will prevent you from missing -- but any +hit over that amount is wasted. (After you've negated any chance to miss, +hit gear does nothing for you.) For those of you interested in the elusive amount of +hit you need as a level 70 fighting boss-level monsters, Coriel over at Blessing of Kings
has compiled all of the necessary data for you
, taking possible talents and different weapons into consideration.