I have been through the game twice and I haven't found anything above 9. It is a funky system. Even if you level up to level 9 disarm you still only have a 40% chance. I gave up on it and stopped at level 7 and used a time crystal to open the 8 and 9 chests.
I haven't met lvl 10 chest; my charakter had a lot of strength, so bashing was not a problem; also my disarm skills were over 10 - so lockpicking wasn't a problem too. I learned from here the trick with timestopping - nice advice!