I completed the Thirsk hall quest in favor of Nords and yet Thirsk hall is always under attack by Rieklings, even after completing the quest. The NPCs seems to be essential so I'm not woried about loosing any of them. I'm rather annoyed by this constant repsawning of the little blue pests every time I go visit the blacksmith there.
I wonder if there's a work-around or something, maybe with the console. The quest ended fine, as far as I can tell.