As it is, the hammer charge attack is one of most unrewarding, unforgiving, dangerous and pointless charge attacks in the game.
It pushes you right into the enemy, has to attack twice which means you're helpless for those 2 attacks, does damage equal to 1.5 of the normal hammer combo and the knockback isn't nearly good enough to justify using it for that. (As opposed to say leviathan.)
The only thing its good for is trolling AFK players by pushing them onto spikes.
I have a very simple suggestion to fix most of these issues.