Pretty sure that's Earl Slick on guitar. Babd is solid. I wish the audio was better but, oh well!
At least we have the video.

when Bowie was a wreck on drugs:

In 2004 he sounded much closer to the studio track:




Fascinating and incredibly long analysis of the album here:

https://thequietus.com/opinion-and-essays/anniversary/david-bowie-diamond-dogs-album-review-50th-anniversary/

EDITING to add that the journalist who wrote that also did a very long review of Scary Monsters here:
https://www.classicpopmag.com/2021/09/making-david-bowie-scary-monsters-and-super-creeps/

Because '74 was the tour where the live album "David Live At Thd Tower Theater" was recorded.
And I find that album to be loaded with solid performances.
Maybe the dope had him erratic, but not a total wreck.
BTW: I believe 1974 was the first tour Earl Slick was in thd band. He & Dave were friends for a long time.

after the Tower Theater shows recorded for David Live. Which didn't get very good reviews: https://en.wikipedia.org/wiki/David_Live

I'd better go check what Tony wrote about it in his bio...

OK... Tony didn't like the album. He thought it was poorly recorded. He hadn't recorded it himself, wasn't there for those shows. He doesn't name who was responsible for the recording, but he does name the mixing engineer he worked with later, whom he apparently didn't get along with. Eddie Kramer told David and Tony that he was the only one who understood the mixing console at Electric Ladyland well enough to use it.

Tony remixed the album for Surround Sound in 2004 (released in 2005) - "microscopically scanned through the sound files and corrected every abrupt change of volume and sound that the recording engineer made back in 1974."

Do you have the original mix, or the one Tony did?

and cocaine, going without sleep for 3 days or more at a time, hallucinating as a result, having an indoor swimming pool exorcised, and saving his fingernail clippings and urine so they couldn't be used for spells against him.