More important role of the geomancer will be later on to replenish armor.
Use skills with friendly fire like impalement as opening skills, before your melees are in close range.
With 3 physical damage dealers the mancer will be more of a support char anyway. Perhaps learn him hydro to for skills who replenish magical armor for example.
Geo does not work that well alone, without any kind of fire source to make stuff explode, though fire is risky for your melee guys on the other hand.
