The thing about Elites is that the Elites, being larger, will be much easier targets to hit (I am assuming the hitbox will be changed, as right now the Spartans and Elites have identical hitboxes, so there are actually some places in the Elites where bullets pass through - most notably the neck!), so it's not like it'll be especially unbalanced.

Also I just want to say that the new Spartans look infinitely better than the ones in Halo 3.