Edit: May 8
Jagex update Dags so they are less aggressive, the xp/hour has gone down by a lot.
Will post more information/possible ways to get more xp later
500K+ Mage/Def xp/hour at Dagannoths PLUS 600+ charms/hour
Dagannoths (Level 112) at the Waterbirth Dungeon give really good mage experience and defence experience. Along with that, you get A LOT of charms with the Charming Imp.
The Charming Imp is a dungeoneering reward which you can buy.
It requires level 21 summoning and 21 dungeoneering to buy, and a total of 100k reward tokens
The Charming Imp is VERY helpful with this method.
You can toggle the imp to choose which charms you want the Imp to pick up for you and the charms you want it to keep.
With this method, Tell the Imp that he can keep the gold charms, so you can keep the crimson, blue and green charms.
Also, since you are allowing the imp to keep the gold charms to himself, you will get 4 summoning experience for every gold charm he will keep.
Getting there
You can teleport to waterbirth Island if you have 72 magic, and be on the Lunar spellbook.
To sail to the island, players need to complete The Fremennik Trials.
Players who have not completed the Fremennik Trials quest can go to the island by starting the quest and paying Jarvald (In Rellekka), a fee of 1000gp.
Setup + Inventory
Set up is pretty much self explanatory.
You have to bring decent mage armour.
Virtus, Ahrims, Subjugation, ganodermic/grifolic work.
Offhand can be a orb, or an arcane.
I highly recommend a master wand, since it is one handed, and has really good stats.
Again, you can replace any armour Im wearing with the other listed above.
We will be using the spell, Rock Barrage Requires 88 Magic
2 blood runes, 5 earth runes for each cast.
http://runescape.wikia.com/wiki/Rock_Barrage
The area is multi, so they will all attack you.
You will be using soul split, to heal.
I know this guide was done in a rush, and may not be the best.
But I hope it helps. Post any questions/comments. Thanks