BRD is the most epic, well designed instance I ever had the pleasure of completely running. The whole instance looks amazing, feels amazing, and the place is so..huge. I have never felt like I had more of an adventure in the whole game than when I ran that place completely through at-level in early WOTLK before they nerfed the crap out of it (and before LFD). The wipes, the runs back, the epic moments of narrow escape. It was probably better that I was the tank and I was leveling with a healer friends, but besides that...
I really wish I would have played in Vanilla :/
My most fun PvE experiences would definitely have to be the first few months of WOTLK. Culling of Stratholme was actually what made me buy WC3. Around the time LFD came out I think I progressively got more and more bored with them. I wasn't drawn to Cata heroics at all, and I'm not feeling MoP either.