Just a friendly tip from your mage buddy.
Keep a stack or two of Major Shadow Protection Potions in your bag and always keeping your life / mana pool above 50% at all times in the open world will help you kill mostly every warlock.
On Sulfuras Alliance they are quite affordable… definitely worth the money instead of
having to walk a few minutes back to my body.
My main is a mage and I have problems against Warlocks with the Felhunter’s but usually only when I forget to pre-pop a pot.
p.s. - REMEMBER the soulstone too and get ready for round two!