Hmmmm...
Set up a bunch of buffs for your melee abilities.
Dash in to do a melee combo which recovers MP.
Jump back to unleash a chainspell depending on what buffs/combos were used, consuming massive MP.
Rinse and repeat.

Does that sound like something that might not be the worst idea ever?

Just a little visual note, it seems from the video like the "jump in" skill has the RDM reeling him/herself in with a magic rope or something. Explains how a mage makes monk-like dashes.