My party is
Cocoy,
Plete,
and Northern Ocean

1.
Upgrade pet equips to appropriately typed lv50 legendary gear where possible (epic lv50 failing that) (obtainable from the trade broker or from lv50 very hard mission satchels)
OR
Grind team up to lv60 (same level as Vorpar), replace gear with Lost Grove equipment (from the broker)
(Exotic (lowest rarity tier of lg equip) or Vinethorn are the most likely gear to be there, and an accessible price)
Earth tank> Warden gear, or Tidal Lord gear. Light healer > Pyromancer gear. Air attacker > Storm Caller gear

2. actual strategy:
two phases of the fight
keep an eye on his buffs- when Vorpar starts to prepare tsunami you need to block with all pets (and/or have thorncoat up)
Thorncoat when he's around 40-50 mana
Second phase is minion summon- Vorpar's invincible and heals while they're present
Take out minions asap to disrupt Vorpar's healing and be able to attack him again.