Due to the cumulative costs of stacking skillpoints, it's actually not a good idea to stack them unless you're needing a stat in particular to beat a certain challenge that requires one thing (such as stacking attack so you can beat the dps race of killing some boss after casting focus and 1shotting your entire party, or stacking fire resist against trogdor).
Favoring some stats is definitely ideal since the costs for a character's stats depends on their base growth (for example each skillpoint in attack is cheaper for remilia than it is for patchy), combined with the fact that being % based means you get more actual numbers out of the deal. But I really think it's a bad idea to say, put 200 skillpoints in patchy's magic stat while your other casters magic stats, or patchy's mnd stat, or your other defensive stats in general are below 100. By doing that, Patchy's damage output may double yes, but chances are, your entire party's survivability also got cut in half, because it takes 2 million skillpoints to make her mag go from 200 to 210, and 2 million could give you like 20 mnd/def on your entire party when it's below 80.
Speed is also a factor. Hitting twice as hard isn't as good as hitting twice as fast (once sp becomes non-issue that is. I find it is for me, I mean, I can cast whatever I want as often as I want, and if I run out of sp, it's cuz someone casted djinn storm or destroy magic or something >=P), because if you hit faster, that means you can also switch faster, or focus faster as well. Speed is also more important on trash fights where being able to attack before the enemy is key.
Seriously though, I've said it before and I mean it, the balance of this game is jaw-droppingly impressive. I don't really think there's a "one" strategy or build.
