Well I dont know bout your build and gears, but honestly your level might pull you down, since you will be taking more damage when few level lower than the enemies, as I remember divine is at lvl34.
I kill him easily solo without any creature or summoning, with less than 5 hp potions. Therefore I really cant suggest an appropriate strategy to you. You can either decide to take down the divine 1st, which should the 1 which inflict most damage to you or take down those summoner and healers paladin. Use your summon and necromantic creature to help you with the fight
