I'm Currently Doing the 4 White Mage "challenge" and... it's not that hard. Actually it's a really good party, look what I did versus Kary:
4 shots of FOG2, + AFIR, + MUTE and she was done for.
I could beat giants in the power peninsula when I was lvl 10. Not just 1 time, but 3. + the occasional encounter with ZomBulls.
And right now they are doing really good. They can beat whatever they want. With all their protective magic, they have complete inmunity Versus ANYTHING. Add the Magic Casting Items and FADE and this party is all-mighty.
Why people say this is a bad party? It's one of the best!