Well, with Jade you can easily use Unity instead of COE.
Jade is less tougher without soul harvest stacks than a ht garg though. So unity is a must for HC and Jade.
With Helltooth Gargs you were just unlucky i guess. The only one that can one-shot is Perdition, or Perendi can maul you.
Did you use defensive gems? Esoteric is must have for HC i believe.