Now that Warlock is all fleshed out, I gave that class a good look this wipe. It has a higher difficulty, especially with default gear, but at the mid to higher levels you have a good permanent sustain and pvp ability.
The most prize piece of gear to find for warlock is Magical Healing items, which makes your damage DoTs heal you better as they hurt enemies. If you can get 3-4 pieces of gear with this attribute you are a terrifying dungeon vampire, capable of casting tons of spells with your health (the warlock spell cost) and regaining it fast. Throw in your Blow of Corruption for a nasty high dmg finisher melee strike.
Downsides - you cant' wear plate, you don't have a sprint, and your spells aren't THAT good. You end up somewhere less of a Fighter than a Fighter, and less a damaging caster than the Wizard, which can be tough to balance or make the right decision in critical moments.
One weird thing is that I tend to bank plenty of gold while successfully extracting on Fighter. I tend to grow sentinmal to the weapons and armor, and unless I find something organically in the dungeon, I keep the snowball going. On warlock though, I chase the Vampire Highlander Strahd ideal everytime I extract or have a little extra cash in the bank. I'll be in immaculate expensive vampire gear*, terrifying to behold, with 5 gold left to rub together and a grey cap in the stash.
* reference photo w/ ninja hat off