Also, the fear is the Skaven Sorcerer when faced with a Dragon might do what Sorcerers do when they panic/last gamble/bring out the nukes and push his big red "Summon Greater Deamon" button, which would in this case be a Verminlord.
Try reading the post you quoted one more time. I feel like this is a case of failing reading comprehension, because otherwise I have no idea where this post came from in response to that post.
EDIT: I think I see it. The Besiegers and the Border Prince are both mercs. I meant the latter, with the "Those two" pertaining to mercs. One is a named unit, IE, the Besigers, while the other is just mercs. I meant the Border Prince mercs and the miners can clear Skyre, if that wins. But I can see how that could cause confusion.