Assuming that you're sending the card to a male who has been both ordained by an organized religious body and earned a doctorate in any field of study but usually in this case, a Doctor of Divinity (DD), "Reverend Doctor _" (Rev. Dr. _) is exactly correct.
The correct way of addressing a Catholic priest is The Reverend John Smith, J.C.D. (the initials for his doctorate are OPTIONAL) on the envelope. The head of the letter would be Dear Father or Dear Father Smith, and in conversation, Father or Father Smith (if there are more than one around). You do not normally acknowledge a priest's degrees in addressing him, unless there is a reason, like in a footnote, then The Reverend John Smith, J.C.D.
If the letter/invitation is primarily to the reverend but also her husband: Rev. Mary Smith and Mr. John Smith If the letter/invitation is primarily to the husband but includes the wife: Mr. John Smith and Rev. Mary Smith If it is strictly a business letter and not church related: Mr. & Mrs. John Smith
The man's; Mr. and Mrs. John Smith, Mr. and Ms. John Smith, Mr. John Smith and Miss Jane Jones.
Executive Assistant to John Smith
When you are addressing a letter to married doctors it would be: Drs. John and Jane Doe.
If you were sending a letter to John Smith, MD - you could address the letter to Dr. Smith.
A PhD is a doctor. You address a letter to him Dr. John Smith. If he is married you address it Dr. John and Jane Smith. If she has the PhD, you address it John and Dr Sue Smith. If both have their PhD's you address it Drs, Henry and Jane Smith.
Mr. John M. Smith and Dr. Mary F. Smith is correct, or John M. and Mary F. Smith, or Mr. & Mrs. John M. Smith. One should never become awkward in usage for the purpose of being politically correct. It simply draws people's attention unnecessarily.
The salutation used for the envelope address can be either Dr. John Smith and Dr. Jane Smith, or Drs. John and Jane Smith. If you are writing a letter to both doctors, then he greeting in your letter can be Dear Drs. Smith.
Addressing a Mayor and his wife: Mayor & Mrs. John Smith
Can you use a prefix and suffix both after a person's name such as Mr. John Smith, CPA?
John Smith was one of them...