I'd replace Starmie myself. As the last poster said, Mega Blastoise is better than Starmie in this gen, and the Blazing Chicken does the job with a Life Orb. I'd also consider using Night Slash over swords dance for better coverage [not shadow claw, because then a normal type can switch in on you]. If you DO remove SD I'd also go with Blaze Kick over Fire Punch fir the extra power. Yes, you suffer from an acc drop, but you do get a higher critical chance and a good bit more power for a low accuracy drop.
Edit: You mentioned Gengar. if you're worried about Gengar why not try Chesnaught? He gets spikes, and walls Gengar completely.