It took Destiny's new Rise of Iron Wrath of the Machine raid all of two hours to be beaten. Now Heroic mode's on the way, so let's say two and half? Two forty five for that? Maybe an afternoon for a three man team showing off.
So that's the new Heroic mode arriving on November 18 with the official blurb saying:
"Have you ventured deep below the Plaguelands to destroy Aksis? If you have not, there is still time to increase your Light, form up a dream team, and embark on the mission. If you have completed that mission, the truest test of teamwork and cunning is yet to come."
For those that don't Raid then the Heroic modifier means more, tougher enemies, because that thing wasn't hard enough already. As with the Raid's original launch Bungie will be watching and waiting to celebrate the first team to win.