A Magic Finder is designed to farm, of course. But keep this in mind: the chance to drop a high tier unique will be almost the same with 100/400 than with 0/0 (due to the small chance to drop those hi-tier uniques). The main purpose of farming is to become a yellow-drop-machine so you'll get a lot of minor currency to convert to Alterations, Jewellers and Fusings, and more some minor tier uniques