There's something about a lens in your collection that never gets used and is, as you say redundant, that gnaws away at the back of your brain. The 85mm 1.8 was like that for me.
I feel like I have just the right amount of overlap between the zooms now with just a few choice primes at carefully chosen focal lengths. Finding those focal lengths was (is) a bit of a mission though!
Having the 135L I often wonder if I would also benefit from the 100L or if I should swap. Focal length wise the look is kinda similar and potentially the 100L could kill two birds with one lens. Portraits and macro. But there's just something about 135mm @ f/2 that is soooo creamy and bokehlicious that you just can't give it up!
Keep them both I say.
I remember the first time I heard about the 135L. I couldn't ever imagine paying that much for a lens... especially at 135mm.