Weapon attack speeds are based on how quickly they cycle through the Fire state (unless you rename it to attack or something like that.) This state can be identified from the others by the segment:
stateFire[#] = true;
# would be replaced with an actual number, usually 2 for most weapons.
In order to change how quickly the states cycle you need to change the following code segment:
stateTimeoutValue[#] = ###;
Make sure the # in the [ ] is the same as the one you found the stateFire[], assuming that the delay comes from the fire state, if it does not, change other timeout values after the fire.
The ### is a number that represents the delay in seconds. (1.00 is 1 second)
Lower timeouts in the sword item to increase its rate of fire.
(I don't have access to my Blockland files atm so I can't physically check the exact Weapon_Sword details, so this is just a generalized guide on how to do this for any weapon.)