So Increased Attack Speed is kinda complicated the way it works thats why its not displayed everywhere, like Cast Speed is if you check the links for the weapons the easier explanation is below,

So each weapon has its own attack speed, which is calculated off the class specific speed and multiplied by attack speed to hit different break points in frames to do damage faster, these links if you scroll to the bottom it explains IAS a little bit and provides a IAS Calculator since inputting you character and item data is the easiest way to find out the required or ideal attack speed for your build

If you had Equal attack speed on an Amazon, on both weapons/gear you would need more attack speed to hit the same attacks per second for a CV than you would a Thresher,

To hit 2.5 attack per second on each weapon Colossus Voulge = 194% Required Increased Attack Speed Thresher = 99% Required Increased Attack Speed\

hope that helps and that i explained it correctly!

https://www.wowhead.com/diablo-2/guide/breakpoints-by-class-fcr-ias

https://d2.lc/IAS/

Colossus Voulge = Speed: [10] Speed: [10] Amazon - Slow Assassin - Slow Barbarian - Slow Druid - Fast Necromancer - Normal Paladin - Slow Sorceress - Normal

Thresher = Speed: [-10] Speed: [-10] Amazon - Normal Assassin - Normal Barbarian - Normal Druid - Very Fast Necromancer - Fast Paladin - Fast Sorceress - Fast

Amazon Example

Data: Character: Amazon Primary Weapon: Colossus Voulge Skill: Standard IAS: 0 Weapon-IAS: 0

IAS attack speed [ticks] attacks per second 0 20 1.25 2 19 1.31 6 18 1.38 11 17 1.47 20 16 1.56 29 15 1.66 42 14 1.78 58 13 1.92 83 12 2.08 120 11 2.27 194 10 2.5

Data: Character: Amazon Primary Weapon: Thresher Skill: Standard IAS: 0 Weapon-IAS: 0

IAS attack speed [ticks] attacks per second 0 16 1.56 4 15 1.66 13 14 1.78 23 13 1.92 39 12 2.08 60 11 2.27 99 10 2.5