Part of mentoring is explaining, "On NA servers it's customary to use /partyfinder for extreme primals even if you want to do them syncked." Many of the people who queue up for EX primals fall into three categories:

A) They don't know /partyfinder exists.
B) They think /partyfinder is only for unsyncked runs.
C) They don't care, you don't pay their sub.

You can't do anything about (C), but simply saying what I quoted above will bring the party finder to the attention of (A) and (B) people. If they ask why, something like, "Extreme primals have some strictly scripted mechanics that need to be dealt with in a coordinated way. You won't find the coordination necessary by using duty finder." This is especially and most visibly true for Ramuh EX and GKMMXII EX; if the roulette is one of these, add "Especially this one; it requires the most coordination out of any of the ARR primals besides [the opposite one]. Queuing up without a party that knows what to expect and how to handle it is asking for a bad time."