Regrouping costs are way off. I need to find a target with 300k+ oil just to cover my costs. If I ignore oil as an asset I can only launch an attack every 18+ hrs, a figure which will only increase with unit and support upgrades. This hardly encourages me to login frequently or stay in the game any length of time. Either reduce regrouping costs, increase oil production or introduce a skill that incrementally decreases regrouping costs as trained.
Just some thoughts (be gentle, I bruise like a peach)