Chosing a merc polearm

I read some guides about this but I am still confused. I know, general rule is "get a Tresher for your merc, is faster than a CV and the overal damage is better. Put G Face and Fortitude and you are king".
My specific question is for my bowazon who use a faith bow with level 15 fanaticism. In this specific case, what is the minimum IAS that I need to put on my merc to get the fastest attach available ?

so , I need some help in this matter, thank you.

 

I am not sure if I am correct, but this might be what you need, assuming you will put Thresher on your merc a provide him 15 lvl Fana



source: https://diablo3.ingame.de/diablo-2/calculatoren/angriffsgeschwindigkeit/?lang=en