War isn't broken, it just has a heap of requirements before a siege can happen. The civ that is going to siege you has to know you are there, like a scout has to have seen your site, or a member has to have come for a tavern/library, or they have to heard rumors or something of you being there. Then, they have to be aware that you are worth attacking, same deal as before, but recent enough information that they see you have dorfbucks. Finally, they have to actually march an army to you.
If you are summoning succubus traders, but the succubus civ is unrelated to the traders(I don't know how the trader summons works, do is actually pull from a civ or just magic them up?) then the civ itself would have no reason to send an army.
Basically, war is now hard and sieges are difficult to initiate.