Can you adjust those drop rates for key frags ?!

Seems to be a common complaint of too many of one and not enough of the other (I could use a few chests, but I've only got a few champs). Why isn't it set that you are more likely to get a chest on a champ that you haven't gotten a chest on, followed by a key? And if you have more keys/key fragments then your chance for a chest (vs a key fragment) is increased, or more chests than key fragments and you are more likely to get a key fragment than a chest.