The +4/+4 is for creatures in a flooded area. It is irrelevant for singularities because they will simply die.
Fixed for those that couldn't get the irony.
The only practical use seems to be Mutation/Improved Mutation.
Catapult and Druid are ok but they have to be there beforehand.
And Chimera+AM is too unreliable/expensive, aside from some obscure OTK deck.
Btw, I tried with GP and it is definitely not an option, they tend to multiply too fast.