Yes, rotating your forces works very nicely... also, something you might not know: I believe the raider trait removes the 100xp cap for barbarians, as you get the one extra experience regardless of xp cap. I believe a certain spell (Valor?) does the same thing. And does having a Great Commander attached do this, too? I'm not entirely certain about any of those methods (as I haven't tried them yet), but I think they work. Might as well give them a try.