Sills (you say rockers for reason best known to you!), front and rear of rear wings (fenders!) in the door shut areas, anywhere under the floor....above the tc and tranny seem particularly prone to the old golden body lightener. Ive seen a couple with the front edge of the roof and bonnet (hood!) suffering with tin worm but this may have been from leaving chips and damage untreated. Best way to stop it???? Import a Euro spec body shell from Europe which were fully galvanised from new and transfer everything frtom your car to the new shell! That might be a bit expensive so you might prefer to paint the entire underside of your Jeep with rust stopping paint, flood your sills with waxoil (or whatever the US equvalent is) and make sure you keep on top of stone chip and trail damage repairs. The rear arches rot out from the inside and short of drilling holes from the rear to treat it there is not a lot you can do about it except repair it when it happens.
If you can't fix it with a hammer, you've got yourself an electrical problem!