I can only talk about how I felt; I may have been completely wrong in my evaluation. But here it is!
I felt both Loadbearer were no-brainers: I had to take them as soon as possible. They do not really help you score a victory like the wards and breaker abilities (both letting you keep more cards in your armory to keep fighting), but they definitely help you gain Knowstones. They also makes pretty much all other abilities stronger, especially the Pathfinder/Lorefinder/Quartermaster. Once I unlocked them, I was very often able to beat the Knowble in front of me and know how I was going to gain the next one. Maybe make Master-at-Arms a prerequisite to Loadbearer II?
All the Breaker abilities were also no-brainers, but I could not unlock them before a couple of games. As soon as I could, I did. Same for Sunderer, but I did not play enought to gain the Cruel Kings Club feat. I liked this.
On the contrary, I felt the active abilities were not worth the cost in comparison to the passive abilities.