This is correct. If you could hold it down like a plasma pistol then it would be overpowered. But if you do happen to charge it up and not time it right then you will miss and most likely not when the gunfight with a pistol. So it requires some skill and it is somewhat risky to use. So I think that it is pretty balanced because there has been plenty of times where the person that is attacking me misses me and I can get an easy melee and I only have to sacrifice my shields for a moment.