Don't get me wrong, I like Tigranes the way he is now, even if he is a blatant adulterer. However I believe he needs some more traits to make him more... unique.

King of Kings (Shahanshah, if you will): Tigranes at this time had taken the title from the Parthians after campaigning as far as Ecbatana. It would probably give him a large influence bonus and can only be lost if Armenia is destroyed, since his son retained the title and only lost it when Cleopatra slit his throat. Perhaps the Parthian faction leader can have the trait "Not the Shahanshah" which severely reduces his influence.

Living God: Tigranes declared himself to be a god in living form. (his unusually long life, 90 something years is suspicious...). This was accepted by all his subject peoples andeven the nakharars. Perhaps another influence bonus as well as a morale bonus for troops, since they would probably be more comfortable being led by a living god?

I'll see what else I can come up with.