Reports duration of combat, damage dealt and dps to the frame of your choice when you exit combat. Should be pretty lightweight compared to most damage meters since it makes use of statistics instead of combat log events.
By default this reports to UIErrorsFrame, that can be changed with this: /run dmgrprtsv="frame" frame can be any frame with a AddMessage method C=.
Here's a few frames you may use:
These might also work: