*Minor spoiler*
This is story related and cannot be missed.
Once you have finished in Downtown, New Repugia, the Repugian Elder will give you the key to the Dental Compound. As soon as you walk through the gate a cut scene will trigger and you have to fight Ophirion, so make sure you have the costumes you want to use selected before going through.
The wizard and pterodactyl will be good choices here as they are strong vs. monsters, Conversely, the clown won't be great, as it is weak vs. monsters and even though Ophirion has a lot of health you shouldn't need the healing, but if you are worried about healing, take the pharaoh, not clown. Realistically, you should be fine with 3 hard attackers, so take the wolf, superhero or jefferson with your wizard and pterodactyl and you should breeze through.
Hope this helps!