Uhhh, there is an advantage in having a more balanced charachter, and cross class skills do come into this. Just because some people dont like those playstyles doesnt make them worthless. Really it is a case of people wanting to be the best at everything.
Kilta is actually right, the plan was, your physical level /stat allocation decides who your charachter really is, your discipline is what your doing. The reason they have caps on how much stats effect you per ranks is so that you have reason to distribute your stats around, its also why there is diminishing returns at high levels of one stat. And yeah, cross class skills are less effective than main class skills, but the +10 ability skill is a very noticeable boost, chakra goes up very noticeably, and recast drops a lot, and honestly before, this was probably supposed to be only the first increase in subjob effectiveness.
There are certain things you just cant avoid, like lack of mattack on a weapon, but they could have added certain weapons that have midranged mattack for these playstyles.

My guess is a mostly balanced person making use of the trait switching systems, can get a fairly good performance on multiple jobs, The whole idea is that you can specialize, and you will see some improvement, but it wont be a direct correlation, the truth is they would have expected people to be way more balanced than most chose to be.


Also the system allows you to change your stats, if you made a mistake, or if you decide long term you want to be a different ttype of charachter, but its not made to make you go from being the best archer to the best conjurer to the best pugilist. The system is only really bad for min maxers, who want to be able to do everything. Its also why they are mad that thier stats have diminishing returns and soft caps.

I agree though it would be better if every stat had more effectiveness for all jobs, more use for some int on pug, or some str on con