Are you sure about this? When we were working on our first kill i timed it at four minutes even and it was still four minutes before i took a break for the holidays. I am wondering if they ninja nerfed the 8 man enrage timer when they nerfed the 16 man.
In our kill video
from a few weeks ago, he drops down at 5:23 and dies at 9:08, meaning we would have beaten a four minute enrage timer by 15 seconds. There is no way we could be beating the enrage timer by 105 seconds; on our first kill he actually enraged long enough to attack me once (yay dodge!) and our DPS certainly hasn't been able to shave the kill time by a full 30%. They're good, but not that good.
That being said it could be 5:30 now; I have no way of testing unless our DPS intentionally fails, which we aren't going to do.
Adding 90 seconds seems like way too much of an overnerf to me. You could kill him with 4 walker phases with that long of an enrage.