Energy Strike may be weak at the beginning but its damage increases with your magic level and level.
With practice, you will be able to aim more quickly. Once you master it, it will become very useful because it doesn't use much mana and it hits far more than a HMM. With a high level and magic level, hits over 200 are easily possible. Even at level 30 you will be able to reach hits over 100 with a good magic level. Damages for the same as Flame Strike, Terra Strike, Ice Strike and Death Strike but with a different element.