/SCH does help in certain aspects, but I feel the utilization for /SCH as a GEO is extremely underpowered. No native enfeebling skill and only access to Sleep 1 (why this is, I have no clue) makes crowd control tough. You should be able to land nukes, SCH and GEO have the exact same elemental skill rating. Dark Magic I capped on my DRK, but I would just try spamming Drain/Aspir/Bio/Absorbs on worms in eithe Aby-Uleguerand or the IT++ Worms in Gustav. I can't guarantee that will give more skillups though, but might as well try it for curiosity's sake. *shrug*

And the way I see it, Geocolure spells seem to have a casting time similar to Summoner's. If you're fighting squishy trash mobs, yeah, I could see that. In that case, it's not going to be worth casting, especially if the party's mobile. On Boss NMs, On the contrary.