At the time of my laparoscopy, my doctor was not able to get a biopsy. Is the physical appearance of endometriosis adequate for diagnosis?

Generally. Biopsy is best but visual along with the typical symtpomatology is adequate. The most painful lesions, however, are not the most obvious & we can only see 65% of the endometriosis that may be present.
Biopsy endo. Endometriosis may look like many other things especially atypical endometriosis, for which reason a tissue diagnosis is very important to accurately diagnose the disease.
Not always. Excision of endometriosis is important for the diagnosis since other conditions (endosalpingiosis and hemosiderin deposits) look similar. You could be referred to a specialist who can do the resection.
YES. Endometriosis symptoms and seeing tissue suspicious of it during a laparoscopy is adequate for a diagnosis. If it is not very severe, there will be less, endometrial tissue to biopys.