[Endoperez]

In addition to things others have mentioned, I have always been eager to try Sailors' Death (Thaum. 3) and Bone Melter (NW mix in Alteration 5), both with very good damage (decent armor-neg. or death) with magic resistance save. I don't think they will work well against SCs, but Vine Ogres or similar, easily massable low-mr troops should go down.

With water, consider the options other paths give you. Water-Earth gives Rust Mist and Jade Armor, Water-Fire Acid spells (unresistable evocations that destroy armor!), Water-Air has frost cloud or somesuch, Water-Nature gives aforementioned Bone Melter. Water-Blood gives Frost Fiends and Ice Devils, neither exactly easy targets.