I know I am very late with this one, especially because iTryToHard has sent me this a long time ago, after taking the trouble of measuring it. So all thanks to iTryToHard/IDeka for this experience method!
By playing BG normal, you can farm about 1200 experience per game, of course it partially depends on the rewards gotten after the game too. With an average of 2:30 minutes per round, this will take you about 10-15 minutes. It is 2 minutes from the timer and the other 30 seconds is an estimation of the time needed to kill the boss per round.
Of course, I am not gonna make a video of this as BG normal is easy to finish and solo.
Imo, this is a good way to farm experience as it is less boring than rescue solo experience farm. Another advantage is that you can farm pike nades, euros and other stuff while you are at it too.