Well a week of trying to get a Dire Maul crew to finish it off finally paid off.
Was myself as a 61 Warlock, a 70 Lock that needed it, a guildie 70 lock to use the items, a 70 pally and a 64 warrior. Even stacked like that it was a challenging fight.
So worth it though, I now have level 70 warlocks whispering me going "I need to do that quest, where does it start?" (FYI, it starts at the lock trainer, idiots).
The Dreadsteed is so cool looking, hope Blizzard changes what instances are required though, as it is a huge pita to finish it off what with Scholomance and Dire Maul being involved.
You aren't a proper warlock if you don't have a Dreadsteed.