I like the idea of GEO and I think it fits perfectly with the CNJ class, but I don't see any way of turning the base class into a DPS. I'd make it a healer with some different flavor.

Ground based effects: instant cast and you could have two out at a time.
The cost would either be TP/tick (opposite of Bard) or MP/tick but you'd risk running out quickly

Earthen Ward - Increases Defense of party members standing within the effect
Increases potency of Earth based spells when cast within the effect (Stone, Stone II, Stoneskin)
Zephyr Ward - Regen ground effect
Increases potency and duration of Air based spells when cast within effect (Aero, Aero II)
Aquan Ward - Haven't decided if it should be Refresh/TP regain (could be OP) or healing potency up
Increases potency and duration of Water based spells when cast within the effect (Fluid Aura, Flood, Spring Water)
Flood - Water based aoe dmg
Spring Water - Restores both HP and MP to target