I think you are on to something Phaelin. In my own experience, I tend to get more experience from battles with more enemies (4 or 5) than I do with less enemies. I also think you get more experience when the whole party is fighting, as opposed to setting everyone to guard while Lloyd goes berserk.
Right now I am using a party of Lloyd, Genis, Raine, and Presea, but I may change it up some to see what works best.
"Only the living have the privilege of saying they'll fight to the last breath. Words like conviction and resolve don't mean much to a dead man." ~ Raven
Frosting is the magic that turns muffins into cupcakes.