Actually new diamond looks more like Fukua. Plus fire variants for Painwheel are both in silver and gold tiers, while there is no gold Fukua. As for 4.9 total of 11 Fukuas are available but 12 Painwheels.
As for balance and PFs changes sound great.
Higher piercing stat decreases armor break damage bonus.
This behaviour is independent from character(at least for Cerebella and Ms. Fortune) and game mode (at least in training and story mode).
Example:
Setup: 2 Cerebellas with 959 atk (no atk bonuses from moves). First one has piercing stat =...