Instead of getting rid of energy system or reduce time recharging. I'd suggest making larger energy storage? Like 3-4 hours storage of energy? Not everyone could sit on the computer 24/7 though. Low energy storage only encourages macro users. All mainstream MMOPG 2.5 D games have like at least 16 hours energy storage. 4 hours is competitive enough for this game.
Is training ground buggy? I tested putting a lv 3 training, after 3 hours without picking him up. He lost all experience and became lv 1. So if you forget to take a lv 15 out of training, he will become level 1 again?