As you're a squishy, I'm assuming you're going to be mobile. This means jump +
displacement + stoneskin for secondary damage avoidance (you can add incorporeal to
that as well with the right gear). Your primary form of avoidance should be mobs being
dead before they can hit you. To this end, you want max. + emp. + the highest SPWR
item you can slot at your level. Get some +15 SPWR pots from House P - every little
helps. I have a L15 Fire Savant whose DBF is doing approx ~480 on a non-crit, non-
save - those are the numbers your should be getting with your Otiluke's.
For soloing, Ice Storm/Acid Rain are very efficient. Ice Storm has a nice slow effect
which, when coupled with WoE, is very useful - even on EE.
Switch to evocation focus - basing your whole strategy around 2sp Niac's is going to
fail. You can lower reflex saves with Solid Fog, Waves of Exhaustion, Otto's etc. to
give you a 0 cost opportunity with Niac's in a rotation.
Your crafter should be able to make greater focus items. Bracers or ring with a guild
slot for SP makes a very nice item. As you're true neutral, a superior stability item can
also be nice (e.g. light mithral shield).
Greater Shout is also very good CC which does not have an SR check and leverages
your evocation DC - as does Electric Loop.
I still think Minos is the best helmet choice at this level (I still use it on my L25) - you
can slot Wizardry or Magi elsewhere.
Frozen Tunic is the best SPWR item you can get at that level and will see you right
through to L20 (upgraded). Without it, your looking at lootgen or Belashyrras Sceptre
I think. As others have pointed out, Infused Chaos Robe or Dragon Touched, if you
have access, would be better body choices.
Don't dismiss Meteor Swarm because you're a Water Savant.