If you aren't using L.Drake set, I would highly recommend Mana Extension Lv7, or at least 4. The reagents are incredibly easy to get in 1-5B. Enter stage, get key from npc, and melee up the reagents lying near the seal stone. Both of the reagents for Lv7 ME are there, so you can spam it without even having to spend much time farming. Easy 1.3k mp every 180 seconds. Plus, its the same reagent for your other buff anyway.
As for where to get the points, I suppose the weakest mything skill is non-rb Call of Thunder, when you consider that it has a 40 sec cooldown, and isn't affect by crit buff either. You could remove a different skill if you wanted to though, like maybe rb Heavens Justice, because of that hefty 150 sec cd and high mp cost.
Other then that, looks fine to me.