99% of the time I stick to a single party which consists of the characters I like the most.

If the story is good enough for that other 1% I might switch in certain characters to be "story appropriate." Then again, I never use Jr. in Xenosaga Episode III, even when I should be using him on Abel's Ark so I guess I'm full of crap.

But yeah, FFXII was kind of a problem for me at times during my first run because all I used was Vaan, Penelo and...ehhh Ashe I think. I never use Fran, ever. Anyway, during the occasions my party got wiped I had to cycle in the useless B-Team who were like 20 levels behind my A Team. It was such an exercise in futility and I wish they had just given me a game over after my first team all died.