I got deranked for not playing for two days last week, was at the blue eyed skull and it brought me down to the crossed bones.
I don't think it's based on grief though, I have 1933 minutes played on Tranzit, 897 on survival, and 239 on grief. I got to the blue eyed skull way before playing grief.
On the topic of zombies, what are your guys' stats?
Here's mine:
