I wouldn't say /SCH is the best sub overall, and definitely not if your playstyle is pure MP conservation. /RDM will always reign the highest in that regard. In my opinion, there is no best sub. S@#% is situational.

I agree, Nuking is very viable supplement damage on SMN/SCH, especially in older content. SMN has a lot of access to Magic Damage and MAB gear. In most older content, I have more MP than I know what to do with if I'm in melee range whacking with my staff for Spirit Taker. If I don't mind the potential of getting enmity or taking a few hits, I will use /SCH. I'll have macros that will swap to MAB to drop a 1200+ dmg helix and/or tier 1 and swap back to perpetuation after cast. If I drop below 1/2 MP. I stop nuking, build TP to 100% and Spirit Taker it all back. I don't even use Sublimation most of the time, more an emergency fluke if Spirit Taker misses and I could use the MP.