And the coolest part about Warlock is how easy it was to level compared to ther classes. Once you had instant corruption, fear, and a decent wand, you were killing as many mobs at once as you could. Fast.
I know that doesn't sound like a big deal, but in vanilla two mobs your level would be all most classes could handle. Then you had to eat or drink. Warlock could take on 4 or 5, lifetap, then drain life lol.
Dude, I didn't start playing until after the BC expansion came out, but the level grinding even then was pretty rough. My buddies got me into it and I was an orc warrior. I had no context so I didn't realize that trying to level solo as a warrior back then was one of the hardest ways to go because without a healer and pretty much no ranged attacks you had to be super careful when pulling mobs and I was constantly running for my life trying to hamstring shit just so I could not die.
My buddy finally mentioned to me when I was almost to level 60 how funny it was I happened to pick arguably the worst class to level with how tough it was back then.