I don't get the point why going heroic as non lvl 69. A 69 healer would at least probably not have enough gear to heal a heroic. And why would someone bring a non lvl 70 to a heroic (even if guildrun)? It really gimp the dps alot, no matter what class.
Even if this work then I would never bring a lvl <69 for my heroic. I rather go with an experied epic equipped 70 grp that will go fast through the instance. And it really isn't hard to get honored with any of the heroic modes today. Revered required some non-heroic instance farming to get to. But now it's only quests and you're revered with all of them.
However, if this "exploit" wouldn't save your heroic run then it would be a really nice one. I would run mech 10 times/day if not even more.
