Damage Taken From Elements
Hemming runs in low health.
Paladins and Mages: Run him around the room while shooting Assassin Stars/Prismatic Bolts/SDs. If he uses Haste, you may need to do the same to keep distance. Make sure to use Exura or Exura Gran if he catches up to you.
Knights: Shoot a Fire Bomb onto the floor somewhere, then attack Hemming and move into the middle of the fire bomb. Hemming will come after you onto the fire, but his War Wolves will not. Thus you will avoid having your shielding broken and will take considerably less melee damage.
Note: Do not bother killing the War Wolves as they will most likely be summoned again very quickly.