Tilbaut Castle is in the top 3 most difficult castles to take, maybe only surpassed by Durrin.
I thought durrin was great until last strat when we found out attackers actually spawn behind the castle not in front where it looks so impregnable. Its actually pretty easy to ladder up behind and above defenders. Tilbaut and rindyar are the two most difficult castles to take. And yes theya re doing pretty damn awesome with a 1.5 to 1 ratio, especially considering ran out of ladders first battle and got griefed with their cmaterial on another. Excellent siegeing!
Considering how expensive siege equipment is this strat (unless you get tons for free from ai fiefs like occitan and mb), its also a testament to their traders to be able to maintain that many battles and sieges.