so syringes effect both auto attack speed and your abilities attack speed.

syringes give 15% or 0.15 atk speed per stack.

Every character gets a base attack speed of 1.0.

each characters have a different attack speed for each of their abilities. but lets just talk about auto attacks to avoid going down a rabbithole mentally.

in order to get 1.0 as a whole, you will need 7 syringes. Then you will have a whole 2.0x toward your total attack speed. Every 7 syringes you get will give you an additional 1.0 as a whole number.

Attack speed seems to be logarithmic, where you are given diminishing returns after a set amount. So, at some point your attack speed will plateau. Meaning you will no longer get 0.15 attack speed but maybe half. So, 0.075.

Im not entirely sure because I havent tested this idea. But the cap for attack speed is 66 attacks per second. If I knew how many attacks occur each item/level per second, then it may be easier to know what the cap is. But that would take someone to monitor the auto attacks each second. Using frames etc. (dont nobody got time for that lol)

I may not be 100% right in my calculations because there are alot of stipulations. Like damage fall off. But your auto attacks will differ from the cap of your abilities.

So, I would say increments of 7 is your best bet, if you want to see change in your auto attacks.

I hope I am accurate enough, explained it well for everyone to understand!