I've tried to search in the forum for the Disarm feat because there are some creatures that are not affected by a succesful attempt of disarming them but I couldn't find any info so I thought I should write here.
For example any of the orcs in the Misty Forest can be disarmed, either if they're wielding maces or crossbows. Also the giants on the Cloudpeaks, those who are wielding those big logs can't be disarmed ((maybe that's on purpouse?))
There could be more, I've just started to use this feat.
Thanks a lot!