Great idea mate, count me in for that Bot run sometime.
I need to make 1 thing clear though, with the exception of 1 instance all heroic instances are the SAME difficulty. A standard melee mob in heroic Ramparts will hit just as hard as a standard melee mob in heroic Mechanar.
Some instances are harder due to the way bosses work in them, for example, Shirrak the Deadwatcher in Auchenai Crypts is a pain in the ass on normal due to his aura that increases spell cast time (which means less heals on the tank). When you go up against him on heroic he's a total bastard, cos he's now chucking 7k fireballs instead of 3k ones and meleeing twice as hard.
Mana Tombs is also considered stupidly hard, because of the difficulty killing the adds that come with the last boss on heroic. They're damn tough on heroic and it can be very difficult to keep up with them.
The 1 instance that I was talking about earlier being an exception from this is Magisters Terrace. Normal Magisters Terrace is only a little easier than most heroics, and heroic Magisters Terrace is harder than climbing the side of a building using only your lips. However, there is some astonishingly good loot to be had in there if you can get through it.
Peace y'all,
Blade/Runes