Mission XP

If you re-run a completed mission will you get the XP along with it, or do you only get it the first time through?

You do not gain any XP you already gained. Although you will gain the extra XP if you get the bonus/Master's for the first time.
Imagine running through Chahbek Village/Cho's Estate/Northern Wall loads of times to get Leg Survivor , that's probably why we can't.

There isnt a lot of point in re-running previous missions for xp,

unless you didnt get masters previously,

or feel that a boss that only appears in that mission has an elite or green you would like

Other than that it isnt reccomended, all you recieve is the xp for any kills.

hope this helps, even though its kinda repeating what Jamster said

Thanks for the info. Guess I'll just redo the ones that I missed a secondary quest in then.