Pielorinho
Iron Fist of Pelor
Houserule time: what about this rule?
Quick and relatively easy, and roughly analogous to flanking rules.
Draw a line from the center of your square to the center of your target's square. If it goes through adjacent sides (but not opposite sides) of a square that provides cover, your target has cover. If it goes through opposite sides of a square that provides cover, your target has superior cover.
Quick and relatively easy, and roughly analogous to flanking rules.