as ettaan said, every 30 stamina takes .25 seconds off the swing delay with a
minimum swing delay of 1.25 seconds(in increments of .25 seconds). So a 2 second base swing rate needs a minimum of 90 stamina to reach max swing rate.
To explain a bit further for figuring out any weapons.
What the code does first is to break the base weapon speed down into units of .25 seconds. For example a kryss has a base of 2 seconds so it would be 8 ticks.
Next you factor Swing Speed Increase from items and skills. Divine fury is 10% and reaper form is 10+ crystal level(max of 16)%.
The SSI cap is 60%
Multiply the total Swing Speed Increase % by total ticks and
drop the decimal.
0, 5, and 10 swing speed have no impact on a kryss
15 and 20 swing speed remove 1 tick
25 and 30 swing speed remove 2 tick.
40+ swing speed would remove 3 ticks
The last step is to
remove 1 tick for every 30 stam you have with the minimum amount of ticks you can have being 5(1.25 seconds)
0-10 swing speed would need 90 stam
15-20 would need 60 stam
25-30 would need 30 stam
40+ would need 0 stam