Ok, finished the battle. Beat it with piloswine, meowstic, lilligant, toxicroak, blaziken, and wiscash.
Strategy:
1. Spam earthquake with piloswine. Take down as many pokemon as possible.
2. Once piloswine dies, switch to whiscash. Either spam earthquake or use some other move to chip at the survivors.
3. I then used petal dance from lilligant until she died.
4. Finished with blaziken for that overkill blaze kick.
Toxicroak is there since I though sucker punch would be good for an easy pick on rotom, but that failed since it used confuse ray. I didn't use meowstic, but consider her backup.
Go beat Sigmund's face in now.