I mentioned this before but I think a good idea would be for 3oC to be a reward from a monthly event. For example, you complete an iron banner match and get a random drop of 3oC, you hit certain ranks for iron banner and get guaranteed 3oC, and/or you can buy 3oC from an iron banner vendor at rank 5 for legendary marks(or another currency). Once iron banner(or whatever monthly event it is) is over, your 3oC expire and/or there's a limit of how many 3oC you can hold at a time. Obviously with some of these changes, you might have to adjust the success rate of 3oC.