Added Smogon and Pokebeach.
I would really like some input on this team though before I get too much done and have to change something.
I'm biased toward Clefable because you can be looking at an entire team of just Clefables and each one is a very different Pokemon, albeit with the same type weakness. For its final move, it all comes down to what you're afraid of most. I'm fairly certain it can learn Psychic, so you can down those pesky Fighting-types and Ghost-types with that. Rock-types are always a danger, so if you haven't evolved it from Clefairy yet, you might want to consider Meteor Mash as an option. Flying-types probably won't be a big deal for you, since Rotom, but Thunderbolt might work.
All in all, it depends on how you look at your team and your style. My Clefable is going to has Substitute, Focus Punch, Meteor Mash, and Thunderbolt. This has good mixed attacking coverage as well as Substitute for deadly Sub-Punching.
All ground types need Earthquake, no exception, so Steelix is good in that department. You should have Rotom waiting in the wings to switch in on Water-types that will try to ruin Steelix's day.
Rotom is pretty good, but I just don't like Thunder Wave very much. I don't know why, it just seems pointless to me. If you can use it effectively, more power to ya.
I have no objections to Umbreon.
Heracross is great, except for Pursuit. I don't like the guessing game it turns into trying to figure out when to use it, but if you can do it, once again more power to ya.
I don't have any outstanding objections to Blastoise either.
Overall, good job.
tl;dr Clefable's last move depends on what you're most afraid of out there, Rotom just needs to watch Steelix's back.