I read up on this thread just before I started the quest, and a couple players in the game gave me tips when I said I was off to start it. But what helped me more than anything was using my 2 teleport magics. Never have tried it before, but it helped me out a lot. I was wondering before if that might be contributing to the insane times people put up, and I definitely think that's a factor. If people were racing you to the gem, you could just teleport over to it. If there was a walk that took 15 seconds, it would take maybe 3 or 4.
It has a recharge time of a minute I believe, so after you use the first one just type "Jump!" when you need to use the second one. Otherwise, it'll give you an error message if you just click on the wand and try to double click on the pin (even if your 2nd magic hasn't been used yet; I tried this out before I started the quest). So, between the answers here and a couple hints that were mentioned in the game (I believe they were also included in the ones mentioned here), I wound up with a time of 7:31. That was my first and only run through. I think I came in 86th, 13 places above where Inferno was. So close yet so far away, LOL! I won a buyable Jolly Roger flag, in case you're wondering.
SO... my conclusion is that besides the mule problem, people are using teleport for the quests and a LOT of them. In theory, they could be using 8 of them, which helps explain some of the impossible sounding times. If you have a pin or two, try it out next time and see if it helps. Certainly helped me, provided you can judge quickly enough whether it's time efficient to use it.