I've gotten to the point where I need to defeat the Vorpar, but whenever I try he just keeps healing, and while I can keep myself alive every time I get him down in health he just heals again, and I can't kill the water elementals quickly enough to do any permanent damage to the Vorpar. Does anyone have any suggestions?

I would recommend looking at this thread.
A quick overview, though:
-Keep an eye on the symbols. Vorpar has a certain effect just before he uses Tsunami, and when you see this effect, use block on every pet, or they'll be stunned.
-When Vorpar uses Planetary Shift, focus your attacks on his minions. I believe he takes health from his minions, but I'm not sure.
-Restat your pets.
- Braelynn could use more intelligence and dexterity, and since she isn't a tank but a supporter, lower her health stat and redistribute those points. Make sure she's on the second or third slot of the party, and not the first.
- Saliya is an Earth-element pet, so she's attuned to the physical defending aspect of the battling. Your Bracelet of the Evoker is completely wrong for her, and she should have her points allocated to strength and agility. I'd recommend one each for agility, health, and strength, and putting her in the first party slot as a tank. If she still isn't quite standing up to the blows, up Health and take away the strength point.
- Star is fire-attuned. Her points should be allocated to intelligence and dexterity, and her gear could be seriously upgraded. She belongs in the second or third spot of the party.
- Rearrange your gear. Remember, for Braelynn and Star, use gear that ups Intelligence and Dexterity, and Strength and Agility for Saliya.
Sorry if I come off as rude. Good luck with your battles.