The guy who posted before is probalby right about mages having some difficulty with macros, but 6 is do-able for most things, as that's how it's been since the game was first released. I can't see them chanigng it now.

weapons skills are generally learned when you reach a specific weapon level. you probabl know this, but in addition to leveling up your job, you also level up your weapons. although there is a limit. for example you couldn't level up your sword skill to 50 at level 1. So in a way ws are tied to your level. Also. each job has grade for how well they can handle different weapon types. For example one job might have an A+ in swords but a D in spears. This grade decides what the maximum weapon level you can achieve for each job level. In the example given, the person's sword skill would be able to go much higher than their spear skill before capping out. Also some WSs are job specifc. I don't have any examples of hand, but I believe that Paladin, for example, is able to get a sword WS that Red Mages can't.

EDIT: Also, I didn't really cover this before but, it's usually pretty easy to cap your weapon mastery for each level as long as you play a damage dealing class. Mage classes have trouble with it though because they rarely if ever attack physically anyway. The trade off is though, it's easier for a mage classes to cap their magic skill, because a white mage of course, uses their magic much more than a paladin or dark knight would.