I got another response last night (the 25th).
Me - “Just to clarify: I’m asking whether on PS4 I need beat TVHM campaign before unlocking Mayhem mode in TVHM. PC players can activate Mayhem as soon as they hit sanctuary on TVHM without playing through the campaign. Right now on PS4 players have to beat TVHM before they can activate Mayhem mode in TVHM. So which is the intended behavior? And why is the behavior different between PC and consoles?”
2K Support - “This is a known issue. Unfortunately, there is no known workaround to complete this mission. Though the final mission is unable to be completed, this should not block any further progress of side missions, Circle of Slaughters, Proving Grounds, or Mayhem mode. 2K and Gearbox Software are working towards a solution. This only occurs in TVHM.”
“Bug: OAK-219830 - The Eridian artifact is unable to be placed causes the mission blocker when progressing “Divine Retribution” under TVHM in Sanctuary3_P.”
“Let me know if you have more concern.”
I don’t understand where that response came from. Either they didn’t/don’t understand my question (I felt I was pretty clear) or they were avoiding actually giving me an answer… I’m going to keep pressing them about it but we may just have to wait this one out for a while, guys.