I've done a lot of mentor roulettes and it's been a largely rewarding experience. In many cases I have provided meaningful guidance to new players and returners with the overwhelming exception of almost all Extreme primals.

ARR and HW extremes are designed for skilled players to learn over multiple hours and execute as a team; not for a group of novices to pug, learn, and defeat in a 60 minute time frame. As a mentor, I always explain each fight's mechanics, but inevitably groups wipe, become frustrated, and fall apart.

All other content in Mentor roulette is casual content that lends itself to successful Mentor-novice interactions. Why are Extreme fights included on Mentor roulette at all? To help finish quest chains? That's easily taken care of by unsynced Party Finder and Wondrous Tails.

Maybe a new "Extreme" roulette can be added for old Savage raids and Extreme primals, but including them in Mentor roulette just sets up situations that are unsuccessful and unfun.