My static party was Squall, Rinoa & Selphie
Maybe I'm lucky but I got "The End" a lot (it still makes me chuckle ^^)
Even if you can control statts (which I love about this game) there still are some differences between the characters, so usually I end up using Squall for fighting Rinoa for curing and Selphie for casting
And imho there limits are far from useless, they saved me a number of times, the first time playing through I did the end boss fight with squall at lvl 47 being my highest and the rest being about 40, with pure luck Rinoa's limit got me through^^
And while at level 100 it gets a lot easier, their limits are still very useful imho