Heroics help

Heroics have rep-nerfed in 2.3, but they are still the most difficult 5man stuff there is. One hits on mail wearers is common. Anyway this thread at wowinsider has some help. Plus here is a guide someone linked in comments, and here is another collection of tips.

Borrowed and reprinted here is a table representing heroics from easy to hard.

Easy: Pens, Vaults, Mech, Ramps(1), Crypts
Easy-Medium: Underbog(2), Seth Halls, Furnace(3)
Medium: Botanica(4), Shadow Lab, Arcatraz (5)
Medium-Hard: Durnholde, Mana-Tombs (6)
Hard: Black Morass (7), Shattered Halls (8)

(1) Don't bring more than 1 melee DPSer, it's not worth the pain on Omor.
(2) Bring somebody that can CC elementals, eg hunter, warlock, or even mage (snare kiting). Can be done without, just painful
(3) Bring somebody that can CC things in combat for Broggok. Also have either a hunter or warlock in group for megahit demon packs before Kel'dan, which are nerfed in 2.1.
(4) AR on the tank for robot pulls- amended in 2.1. Some form of defensive dispel (priest, paladin, felhunter) is required for 1st boss. 3rd boss (Thorngrin the Tender) is doable but a major pain and not really worth the effort, fixed in 2.1. Shadow Priests trivialize much of the instance.
(5) Zereketh is very hard and SR on the tank is recommended. Bring 2 healers for Skyriss.
(6) SR on the tank for Pandemonius. Melee DPS is largely a liability on both Pandemonius and Shaffar. Bring tons of DPS for Shaffar, requirements hopefully eased in 2.1.
(7) Bring tons of DPS.
(8) Have 2 or more players who can CC. Bring a paladin, Limited Invulnerability Potions, or a group with KTM and impeccable tricky aggro control for the second boss, hopefully fixed in 2.1.