Your picks of mediocre or lousy vocals with great musicians!

I would also rather hear Lemmy sing his stuff than anyone else. Its a unique though technically flawed instrument as well.

Then of course there is the case of the man Johnny Cash himself.  Often a great but limited and flawed vocalist who probably would be thought  of lesser if any other way.

The Grateful Dead and Phish all members.

Who's the OP? Tater? Totally disagree with the entire theme of the thread. Inferior vocals compared by whose standard? Would Louis Armstrong be considered Inferior?  Kate Bush? Joe Cocker? Is it inferior or different? Or is it just personal preference?

Probably the absolute worst is "Wilford Brimley with the Jeff Hamilton Trio".
I can't understand why Jeff Hamilton did this album, Brimley's vocals are absolutely the worst!

Personally, I enjoy the singing of many/most of the perps cited.  It's that unusual quality that makes the song more charming.  Another example is the Band--Rick Danko and Richard Manuel had quirky voices which I like, but I understand why they are not everyone's cup of tea.  Levon Helm sounded like a country hick but he had a great voice for the material he sang.  They had each other plus Robbie Robertson and Garth Hudson playing behind them, not a bad lineup of players.
As far as Dylan covers:  the all-time fave is Hendrix' version of All Along the Watchtower.  And check out Judy Collins' cover of I Pity the Poor Immigrant, with Buddy Emmons wailing on the pedal steel guitar.