No, it's not literally all that's changing -- it's cutting off access to the hall of brute (Gaddy and I both brought up in posts), which has some of the best cleric XP in game.
Dungeon was added pre-Tirantek, and at the time, it was (in my opinion) by far the most intricate and thought out area. Key from an hourly mini-boss; mini-quest to get the first key; navigate three separate areas of the dungeon which each pose their own unique challenges (blind navigation, mini-mini bosses, mumbles, etc); battle three more mini-bosses.
From ice_cold: "There was an issue of people farming Telatin by simply logging their party on the Plagued Spider, or before the final part of the Gauntlet with all the mini-bosses." --- this was the staff-identified issue.
Making Telatin area log-to-local solves the staff-identified issue of camping Telatin.
Making Telatin spawn rate lower reduces the amount of seals that can be farmed in a day by a party sitting AFK next to Telatin.
Making Telatin drop something other than seal further reduces the amount of seals that can be farmed in a day.
Making Telatin more difficult (now goes invisible, and I believe HP and damage were both raised) accomplishes nothing, imo.
It feels like a chainsaw was taken to the area, when hedge trimmers would've gotten the job done just fine.
And I don't get why a change was made to this area, when the Credenza problem is a much bigger issue and has been discussed ad nauseam. It feels odd that Stig made this change to an area that came out before he was staff, but won't fix the issue in an area he developed.