Lightning doesn't care about people at all, barely factors them in beyond the need to protect the ones close to her. She most certainly makes her choices with Ti. Fits ISTP quite well.
The characters aren't really bland, they are just annoying, lightning doesn't say enough, Sazh whinges too much, Vanille's voice is retarded, Snow's hero act is stereotypical, Hope whinges even more than Sazh, Fang is too cool, lol.
Lightning, E8 - feels the need to be strong, to protect the weak
Sazh, E6 - values loyalty, worries about safety, would do anything for his kid
Vanille, E9 - Wants happiness for everyone, encourages unity
Snow, E3 - confident, determined and showy (he's very into his bro image), wants to be the hero.
Hope, E6 - contemplative, blames his circumstances on others (not 1, 4, 5 or 9), vengeful, clearly not 2, 3, 7 or 8, therefore E6.
Fang, E1 - strong-minded, level headed, disciplined (I only just got up to her chapter, so this is a huge guess lol)
MBTI:
Lightning - ISTP
Sazh - ISTJ
Vanille - ESFJ
Snow - ESFP
Hope - INFP (His hatred of Snow seems very Fi to me)
Fang - ESTP
And what's going on with the super thick Aussie accents!?!!? I take it in the distant future we're going to be "WINNING!".