I've already done some Raiding with Leashes vanilla raid posts. The next logical step would be Burning Crusade soloing, but I've tried and failed to make a glorified loot list more interesting to read, since BC content tends to be more "walk in and win" nowadays than an actual soloing contest.
So, while I wrangle out an adventure in tiers four to six, I will talk about killing dragons solo as a warlock in order to grab dragon mounts.
I'm not talking about dragons that require friends by your side to complete: e.g., Deathwing's two dragon mounts, Ultraxion's mount, completing a dragonstick, or Al'Akir's dragon drop. Al'Akir has actually been soloed before by a warlock, but you'll need friends in order to clear his genie council first. I'm talking dragons you can go beat up by yourself.