Here’s my take on the above terms:
[Canto] 睇病 = (of a patient) see/consult a doctor
[Canto] 睇症 = (of a doctor) treat a patient
[Mando] 看病 = [Canto] 睇病 + [Canto] 睇症
[Canto] 睇醫生 = [Mando] 看醫生 = variant of 睇病
[Canto] 診症 = [Mando] 診病 = to diagnose an illness
[Canto & Mando] 診斷 = (n) diagnosis; (v) to diagnose
[Canto] 睇病 = (of a patient) see/consult a doctor
[Canto] 睇症 = (of a doctor) treat a patient
[Mando] 看病 = [Canto] 睇病 + [Canto] 睇症
[Canto] 睇醫生 = [Mando] 看醫生 = variant of 睇病
[Canto] 診症 = [Mando] 診病 = to diagnose an illness
[Canto & Mando] 診斷 = (n) diagnosis; (v) to diagnose