The post-credits scene in Doctor Strange is an excerpt from a longer scene that takes place in Thor: Ragnarok.
Roughly one quarter of MCU movies have recycled end credits scenes.
The post credits scene from Iron Man 2 was used in Thor.
The post credits scene from Captain America: The First Avenger was used in The Avengers.
The post credits scene from Ant-Man was used in Captain America: Civil War.
The post credits scene from Dr Strange was used in Thor: Ragnarok.
No. The stinger in Ant-Man was later reused and expanded upon in Captain America: Civil War.
Ant-Man was released June 29, 2015, while Doctor Strange was released October 20, 2016.
The scene from Ant-Man was literally taken from the dailies that the Russo brothers submitted to Marvel for them for approval/oversight.
The first instance of a scene being redone like the one from Doctor Strange occurred in Captain America: The First Avenger. This scene was directed originally by Joe Johnston, then when the scene was used in Avengers, Joss Whedon recreated it.