Raynor and Banks courses are difficult to change ... Mr. von Hagge had to bring in a lot of fill at Camargo to mess it up.
I'd agree that a lot of Bendelow's early work was changed completely in later years, because it was built on a shoestring, and not really meant to last.
Off the top of my head, I would say that the two architects whose work has suffered most were Bill Langford and Max Behr. Langford's work was too severe for a lot of his clients, and it was also built very wide, so a lot of his courses like Wakonda and Kankakee Elks have been mangled by tree planting out in the lines of play. Behr's work was very subtle and a lot of it was ruined by adding extraneous features and losing big areas of short grass that provided options.
Ross's courses are generally well preserved by comparison. Yes, there has been a lot of restoration of them in recent years, but most of it has just been fixing bunkers and mowing out greens ... the bones of the courses have been the same all the way through. I'd say the same for Tillinghast and MacKenzie and Macdonald and Flynn.