Flop shows are natural choices, but a couple of hits too consider:
JOSEPH...DREAMCOAT is a case where the show is little more than what is on the recording.
FUNNY GIRL - the cast album is terrific, but the show on stage never worked. (The film version made a number of improvements.)
One other thought - Does listening to the cast recording set up unrealistic expectations for the show? If you know and love the OCR of MACK & MABEL wouldn't any performance be a let-down vs. what you imagined the show to be like?
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com