I think a sound feedback on long swing/ missed swing would help, as would a sound when you recharge a swing after a miss and one different sound when you make a valid swing.
A pain noise would help too because the player's attention is rarely focused close to the character..(you usually look ahead to see if you must jump early to be low enough to kill the next robots, it is really difficult to try to fight robots while above them, often you long swing and you do not recharge, or you take a hit.)