Or the actual reality: anyone who cares about Mentor roulette will do all of them in PF, then immediately bail and continue the same pattern again if they get EX in DF since it's not worth it, making your whole system pointless.
Alternative likely outcome: The EXs never pop since the amount of people that would care to re-unlock mentor roulette with all that criteria would basically be <1% of current mentors, completely defeating the point of your system and preventing you from ever using DF for EX's.
The simple reality is that EX trials don't belong in a roulette alongside things as trivial as Guildhests. If you're that adamant about doing trials synced with your buds, find a group of 7 others or PF it. Nothing will stop people understanding that EXs are a waste of time in mentor roulette and bailing. and if you implement punishments harsh enough for leaving, they'll just fake D/C or not queue at all; harming the dungeons/guildhests/normal trials/normal raids that could use the mentor roulette peeps to fill them out and actually have a chance at clearing.