Thoughts on my leaky bike?

Harken to the words of the XJ guru AME, for he doth knoweth of what he speaks. Amen.
I too suffered as you are many years ago and was never able to effectively fix the problem dispite rebuilding the gear carrier twice with new orings and seals. Even a new cable didn't fix the issue so I know just how frustrating this can be. I hope you are better at this repair than I was.

 

Once the gear housing has had its seal and proprietary o-ring replaced, and even with a brand new cable, you still get some oil "fogging" in that area. It's a really harsh environment for the oil seal.

It's also a really common failure.

I agree with chacal too, if your cable itself has been wrapped with electrical tape chances are the sheath is compromised so I'd replace the cable as well as rebuild the gear housing.