The new questline requires you to beat a boss on hardmode 17 times in a row without getting hit once. It is physically impossible if your connection is anything other than ideal.
I have died multiple times on 5-8 victories purely because of connection. If your latency is high, you get hit by attacks that you dodged because the server does not update your position in time. If you get even a minor lag, you do not have time to dodge the next attack.
Online games are simply not good for such type of challenge. Please do something about it. It was fine while it was a niche easter egg for warriors, but now it gatekeeps unique and special rewards. Either make it 17 flawless victories in total instead of back to back, or make it doable on lower difficulties to allow for lag