I think another thing to do here is to take a note from some - though admittingly very few - RPGs, and remove combat experience altogether. Crazy? I'm not done yet. Experience would come from achieving goals, and only from that. There would still be fights, no doubt, but killing wouldn't be the only way to accomplish things. Need a magic chalice to save someone's life, but it's in the den of a fierce dragon? Fighting man kills the orcs, priest turns the skeletons, bard/wizard knows exactly what chalice you need, rogue sneaks it out from under the dragon's nose.