Treadshot, Ground-types (other than Water/Grounds) really won't like Starmie, due to their generally poor Special Defense (plus Ground is weak to Water AND Ice, so even with a resistant secondary typing, you're still taking a STAB hit from Starmie's Surf). No Water/Grounds learn Baton Pass, so unfortunately, if you insist on everything on your team having Baton Pass, Vaporeon's about the best you're going to do. But unless you've set up a few Calm Minds or something, Starmie's probably going to 2HKO Vaporeon with Thunderbolt (guaranteed with Life Orb), while Vaporeon only has a decent shot at a 2HKO with HP Electric (although you can guarantee it with Stealth Rock damage or some Special Attack EVs). You're fairly screwed in that matchup unless you predict Starmie's switch-in, because obviously, Starmie outspeeds Vaporeon (barring a bunch of Baton Passed Agilities on your side).