Hence why we are here Noble, this is the reason we are having this conversation. I have only had a few guilds that still do this. Luckily the guild I am in is power enough to keep the enemy locked down to the middle, unless we get Bteam or PPK. Often times they don't have the chance to abuse this. The problem stems from correct AI never being developed. Any monster or NPC, will always take a straight line to the target REGARDLESS of walls. Monsters do it in instances to. It has been this way since they made the game. SO when people send chiron to attack he has no other option then to run straight for the building.
The solution here is new AI. But that's far to involved and difficult or it probably would have been implemented already.
So what were looking at was suggested by another poster on the forums. (Can't remember name

) All buildings should have a debuff. NOT A BUFF, that allows them immunity to everything. The only way to remove said immunity is for any one of the 3 siege gates to be destroyed. Once this happens the debuff stays off for the rest of siege. Does it completely fix the chiron issue? No, is it the easiest solution and one that the community will accept? Yes.
And for the lazy coders out there if there are still some it's easy. Write up another debuff, on the the siege load function put it on all buildings. When the gates disappear, (There's already a function, since the gates have the burning animation.) just call another function to REMOVE the debuff. Since we don't need the debuff to come back it makes its much more simplistic.