- It is good that you have Elemental Staves, that is a start.
- Earth Grip also helps if you are casting Earth spells at your level, but an INT grip wouldn't hurt either.
- A lot of your SCH AF gear really isn't that good for actual playing in. I'd recommend spending a lot of time in Campaign and getting some of the lvl 68 Cobra gear from the past. They have some decent nuking pieces. Just compare and contrast to see which you'd rather have. Also, you'll probably need some help but Vicious Mufflers from the past are nice too.
- Sell those rings and get some INT/MND rings. Of course, INT for nuking/enfeebling and MND for healing/enhancing. SCH is too MP efficient to need to focus on MP+ gear. The same goes for Earrings. There is an NM that drops a really good nuking earring. Moldavite Earring.
- Waist is ok, might be able to find something else.
- Good job on the back piece. +1 if possible, but at this point you've got an upgrade coming soon anyway.
- You've got the right idea on the Tathlum. Could replace it with a Sturm's Report, but that is more MACC than INT.
Ultimately what you're looking for in a Nuke set is Magic Attack Bonus > Int > Magic Accessory > MP. Also, make sure you are casting Sandstorm and Klimaform prior to nuking him if you get the chance (I don't know what you have time to do, never did the fight but this is just standard stuff to look into). Don't forget Tabula Rasa. Make a macro that activates all your stratagems at once (Parsimony, /wait 1, Alacrity, /wait 1, Ebullience).
Overall path of the fight:
- Cast your standard buffs + Hailstorm and Klimaform. Klimaform has a very short duration when compared to its recast so make sure it is the last spell you cast and you are doing Step 2 immediately afterwards.
- When you engage, start out with Ebullience + Cryohelix (or dispel, then helix) with the ice staff equipped. Hopefully the fight doesn't take 1 min, but the extra damage while you do certainly helps.
- Quickly switch back to Sandstorm once you finish casting helix and activate Tabula Rasa.
- Use your Stratagem spam macro and spam your strongest spells! Since you have Sandstorm up, it might just be beneficial to spam Stone III and IV.
- Cure and debuff as necessary.
Macros are your friend.