In addition to keeping them enfeebled (as you know, Silence is the most important), Banish can make a significant difference in both melee and magic damage. Check these out for more info:
Banish - FFXIclopedia - a Wikia Gaming wiki Banish II - FFXIclopedia - a Wikia Gaming wiki
(Most likely only the first one, if you're going for sub job items at the level you would need them.)