Because many decks (especially) aggro/green decks use multiples of the same creature with specific threats such as Tarmogoyf, you might consider Echoing Truth for your SB.
Here is my SB:
2 x
Tormod's Crypt2 x
Surgical Extraction2 x
Echoing Truth1 x
Gilded Drake2 x
Kira, Great Glass-Spinner2 x
Phantasmal Image1 x
Sower of Temptation3 x
Submerge
It is pretty staked vs anything that uses the GY, and Aggro as I have found them to be my worst matches. No it is not perfect; but it might give you some ideas. PS, yes I know that many guys are running Jittes in the SB, mine are main as I don't like Dismember that much, and I have not found that I need more control as I have the spare control in the Main and run the P-Image in the SB, but the meta is always changing so this is a guide and not what everyone should use.
I hope that helps and it was nice to see Merfolk in the top 8's again.