My rolleicord Xenar is as good as the original poster of this thread, although not as sharp at f3.5 as it is at f8. That would just be silly. Randy, I had similar experiences to you. My rolleicord xenar matched or exceeded my Autocord which I sold but wish I hadn't. The Yashinon I had was also disgraceful compared to the other two and I don't really understand the hype for it. Another tessar style lens I've had bad luck with was the voigtlander color-skopar.
Yes, it's about sample variation and luck. I have had Carl Zeiss Jena Tessars that were bad performers. One Zeiss-Ikon Nettar with a 4,5/10,5 Tessar that didn't improve at all by stopping down. The focus was fine and the back lens group was screwed in all the way, so it wasn't a lens element spacing problem. The center sharpness was the same from 4,5 to 22. It was fine for those small prints people put in albums in the 1930's, but not good for enlargements.
The 3,5/75 Tessars on pre-war Rollei's and other cameras also vary in performance. Some are razor sharp, but some are just OK. The 1938 6x6 Rolleiflex on my avatar has a fine Tessar, but I also have a 1939 one with a razor sharp Tessar. The 1938 4x4 Rolleiflex also on the avatar has a very sharp 2,8/60 Tessar. Handy little camera.
The 3,5/105 Jena Tessar on my post-war Ercona is really good. I had the same luck with an Agfa Solinar 4,5/105 and Color-Skopar 3,5/105, equally sharp fine front cell focusing lenses. The 3,5/105 Voigtländer Heliar on my 1938 RF-Bessa isn't as sharp, but it's sharp enough and has other qualities I find lovely (almost 3D rendering). The 4,5/105 Heliar on my Bergheil is both razor sharp and has that "3D quality".
Lenses that are often overlooked are the dialytes on very old folding cameras. Dogmar, Isconar, Helioplan, Sytar and others. They have very even sharpness from corner to corner and are in this regard better than Tessar-type lenses, but have lower contrast and these cameras can be cumbersome to use. None of the big companies made folding or TLR cameras with coated dialytes post-war. I wish they did.
I have a 6,3/13,5 cm Goerz Dogmar on a 9x12 camera, and despite the lens being from 1916 it easily beats the decades older (I meant YOUNGER!) 4,5/135 Tessar and Skopar lenses I have tried.