Iron Guard is a level 12 ability and you need to have it loaded to be able to use the rest of the MA trees. While without it you can load up basic Kung fu, karate and aikido, if you don't load it, you can't load Martial Arts Initiate, and you need that ability to access the rest of the MA trees.
So whether it's worth it or not, if you want to be a Grand Master, you must have it.
