also, avatars could be swapped for some fantasy ones (preferably with characters) with lots of details that could be used as clues)
If anything - I'll join in too, but I'm lost with the roles, though I'd also add someone to the gray mass: you could have characters like a witch, inquisitor, executioner, blacksmith, merchant (or just traders - each with different goods), troubadour, etc. - give them minor abilities, but so that no one is left without a distinct role.
Regarding clues:
1. Maybe the killers themselves can say what clues they might leave? Within reason, of course
2. Maybe leave hints pointing to a larger number of participants? Just some insignificant ones, and others more substantial. (Oh, it's hard being a GM! Zubr, good luck)
On the second point, I'm basically not against having 2 killers instead of 1. But if they run into the king's protection, then both will die:)
P.S. also, facts from users' HeroesWorld lives could be used as clues)

Барон "Vampires"
Отдай свои прошлые сны,
В сомненьях себя обрети,
В бешеном танце душа кружится!
Не думай, что будет потом,
Здесь и сейчас мы живем,
Стань хоть на миг сам собой, слышишь!