From my testing in this thread, AC does have a softcap:
https://www.project1999.com/forums/s...d.php?t=444022
I haven't tested Warriors specifically, but all classes get diminishing returns on AC after they hit Softcap. Shields will raise the softcap by that amount. For example, if your classes softcap is 200 and you are wearing a 25 AC shield, your softcap becomes 225.
From Haynar's post:
https://www.project1999.com/forums/s...8&postcount=13
It looks like Warriors have a diminishing return of 45% AC after the softcap. The EQEMU values I found show that Warrior softcap is at 300 AC.
So in theory a Warrior with 500 AC wearing no shield has 390 AC after the softcap diminishing returns.