Why? There's Vix and Highmarch. Just run over Caligus, try to take lands around Karbala and you can have a new agressive realm at Sirion's doors. I would say Vix has been very successful. The problem is that Sirion is so stable that whenever a kingdom dies, they go straight to Sirion, which makes new kingdoms grateful... well, some time gratitude must goes away. Maybe it's a matter of waiting or changing the mentality of the players. More allies, less war.
I do not know if Sirion being Sirion is worse than what happened to Perdan.