one issue with your calc is that for getting 4 pieces that use 4 wishful resin, you will also need 4 mainstat resin, rather than just 1 for a single 1+4 piece. but i generally think 4 for 2 substats is too expensive anyway. guaranteeing 2 substats doesnt seem very useful if youre also relying on getting good rolls for both of those substats. unless you also use a dice which makes the whole thing even more costly.
one issue with your calc is that for getting 4 pieces that use 4 wishful resin, you will also need 4 mainstat resin, rather than just 1 for a single 1+4 piece. but i generally think 4 for 2 substats is too expensive anyway.
guaranteeing 2 substats doesnt seem very useful if youre also relying on getting good rolls for both of those substats. unless you also use a dice which makes the whole thing even more costly.