Today a guildy induced me to run Heroic Halls of Reflection on my tanking warrior. Sighing, I slapped on my heroic set and we went into the instance (actually, we ran all three ICC heroics) and when we finally got to the Lich King, said guildmate said "Okay, we'll do the ledge strat." I had no idea what the ledge strat entailed, and told him so. He said "go stand over there" and so, bewildered, I did as he asked.
What followed completely trivialized the event. So much so that I'm torn: on the one hand, I hate HoR in no small part due to the difficulty of picking up multiple abominations and tanking them while also trying to get aggro on the spell casting Risen Witch Doctors. The 'ledge' strategy is very simple: let Arthas walk past you and lumber his slow way up the tunnel after Jaina or Sylvanas like he always does. Meanwhile, the hordes of undead he spawns? They come running back to you, even if you're still at the door to the ledge. Since you could never stop the Lich King from getting to Jaina anyway, you don't lose anything for staying behind him, except that you no longer have to adjust in the event that the Lich King is getting closer to you with his aura of hurty.
Even more trivializing is that the further away from you this all moves, the longer it takes for the multiple mobs in the wave to reach you, making it much easier to pick up the various mobs and have them all be DPS'd down before more arrive. I never had more than two abombs on me at the height of the event's last wave, they lumber in so slowly.
Overall, I know two things: I'm horribly tempted to do this event this way every single time, which probably means at the least Blizzard needs to rethink how the mobs path or how the Lich King works, and furthermore, doing it this way absolutely reduces the difficulty of the event so sharply that it becomes much easier than the Falric and Marwyn event.
This strategy is quickly becoming popular and should be considered an exploit, one used to avoid the encounter's mechanics entirely (which is different from Falric and Marwyn where the geometry of the room is used to deal with the mechanics of the encounter, versus avoiding them entirely). We're posting this in hopes that this is brought to Blizzard's attention quickly and a resolution is put forth with all due haste.