in donphan/serperior I'd run zekrom. like someone else said, mamoswine is the only surprise water that you'd need steel for, and it's not nearly good enough to worry about in the meta. so the others are weak to grass and electric, and you already have serperior to cover the grass ones, and zekrom can be electric without having to have electric energies in your deck. blastoise will do 100 to zekrom but then zekrom would take out blastoise no problem after that, or at least get him weak enough to take him out with donphan next turn. throw plus power in there for OHKO or a lost remover to stall to not get shot would work.