I completed the legendary quest and got the cloak on my shaman a few days ago.
I was stuck on the Secrets of the First Empire quest for several months because I got bored with the game after Ash disbanded so I didn’t feel like playing a lot, and if I first decided to play I couldn’t be bothered to run Looking For Raid because the drop rate of the quest items seemed so low and the other players there were usually so bad, annoying and rude that it made me want to just press Alt F4.
But then, months later, I read about the Gaze of the Black Prince buff and I decided to complete the rest of the quest chain because I didn’t really have that much left. I don’t remember how much time I spent completing the Secrets quest, maybe a few weeks, it felt like that quest took the longest time because you had to collect 20 quest items. The Thunder Forge solo scenario with Wrathion was very fun to do again, this time as a healer. I thought it would be hard, but it was very easy. It took me a week to collect the Titan Runestones but after that the rest of the quests were very simple and quick to complete.
I’m glad that I completed the quests and got the cloak now because I read that they are removing it in Warlords in Draenor. So if you’re planning to complete the legendary quest chain on one of your characters, you better hurry up and get it done before they remove it. Wowhead has a great guide which I followed, Mists of Pandaria’s Legendary Questline Guide.