Damage/Attack speed comparison

[muddy19]

I need some help. I am trying to balance some weapons but it seems that I'm horribly off. I need to know about how much attack speed boost would balance out a 4 damage weapon to a 28 damage weapon but i cant figure it out. I'm guessing that i am way too low though. Just wondering if anyone could help me figure out this small problem...thanks.
EDIT: I forgot to mention the attack speed is at 2.0 i need to figure out the % bonus to put on the weapon to balance it.

 

[canons200]

the combat attack cooldown.
1 = 1 attack per second.
0.5 = 2 attacks per second

formula
1 / X = number of attack per second
eg. value put 0.25 = 1/0.25 = 4 attacks per second