Do I have to beat Samman before confronting Demion ?
 

I remember they're soul bonded and there's one NPC that says without Samman Demion would go down pretty quick. Does this mean that I have to defeat Samman first or the fight with Demion will be harder like one of that fight in KBTL?

Well his armies do not change for sure, dunno aobut stats

I also haven't seen any change in both of them, no matter the order.

SHame, would be cool if this would actually be related for real too. :)