Energy is energy. Being able to absorb means all forms and the more energy you have the more damage you can do. This is where the realm of over power begins. Yes he has to stay still and focus but if he is always storing and releasing then he has a lot of room to absorb any big attack. He could lose focus for a split second but then he has weapons to fall back on quickly or taking that absorbed energy and just using it in whatever way he wants.

See what I am saying? There isn't much of a down fall. The only down fall is always having to release energy which isn't much of a down fall.