Could you remove Carbink from that held item? Carbink spawns quite often without any held, bigger problem is with Diancie. Thanks to this change, the possibility of getting Diancie would increase a bit, which right now is very hard to spawn it (and I am not saying it's wrong).
If you decide to remove Carbink and leave just Diancie in this held item, then gonna suggest decrease that 10% chance to 5-8% of boosting chance to mine Diancie.