I think the easiest solution would just be to not let him appear in this quest at all if you haven't done Three vs Eleven yet. The main reason he is in the caste is because the player kicked him out of his temple so if that doesn't happen he has no reason to be at castle Storme.
Having Three vs Eleven as a prerequisite would decrease the number of players that find this quest on their own I fear since that quest is a bit hidden away and players would have to go with both Hirge and Griss as companion while I think most players go mainly around with one (except if they check the wiki a lot).
Also as a side note. I found that the achievement for joining the Three is one of the lowest EK achievements on steam, even lower then joining the mage guild which is harder to complete. Do players just not pick cleric a lot or is it because Three vs Eleven is more hidden then the other guild quests?
EDIT: Nevermind, David already responded with an even better solution while I was typing out this answer.