Legacy .case diacritics?

Am I correct in assuming there’s no use including glyphs like /acute.case if I have /acutecomb.case in my font?

I believe so. I don’t think there’s a need to keep the legacy .case diacritics. Though, I do believe the legacy diacritics (without the .case suffix) should still be kept in the font. Applications may use them to display the diacritic placeholder before applying to a letter. Some of that detail is in the Diacritics tutorial.