The only other thought I have is that your axle or axle tube could be slightly bent, causing run-out that's damaging the seal.
My left rear seal leaked like a sive for a while. When I pressed off the bearing, found out that some brain surgeon used a die-grinder to cut off the bearing, and put a 1/16" groove in the axle shaft. Filled it with a sealer, and pressed on a new bearing, and so far it's worked well. Prolly have to replace the axle eventually.
Erik
