In case anyone cares, I did some easy math and the new Exp. Share gives 1/2 of the XP earned by the poke who delt the last move to the entire team. For example, if I defeat a poke and the poke who delt the final move gets 100 xp, the entire team earns 50 xp.

I know no one will probably care, but just use this for reference when leveling up teams.