Ok. Keep in mind this strategy is designed for a PUG group of largely unknowns. In a guild group or channel group, I would use a more traditional strategy. I have successfully employed it over 10 times, with one failure, in a PUG situation (We were sooo close). Resource use by the clerics was typically 0-5 pots (at level 16). No resources should be needed other than a stack of heal scrolls (you probably won't use 1/2 of them) in current 18-20 level groups.
Group makeup: 2 healers, 1 bard, 1 caster (wizard preferred), 4 heavy dps 450+ hp tanks (good hp barbs are nice), 4 ranged DPS types. When forming group verify roles and ability to fullfill before accepting. 3000+ arrows for ranged DPS types.
Part 1: Caster cleans up ahead, 2 tanks with vorpals designated to clean trash at the main portal, everyone else DPS on portals, keep an eye on caster (if he needs help have one of the healers offensively specced go help, or a vorpaling tank).
Part 2: Old method of pulling outsider to Northwest, Elemental/Cat to the NE, rest to wall in the SE is employed.
Part 3: standard
Part 4: Most people die when the devils come in when you first start and between rounds. They do ALOT of damage very quickly to everyone if they bunch up. Advise them to spread out alittle around the crowd control, anyone less than 400 hp should be well out of the crowd control then come into mass heal range cautiously. Four tanks go in with healers designated to spot heal w/ heal spell and scrolls two tanks each (they should be on opposite sides of Arratreikos). This is particularly important as healers often waste mana in mass heals (this is where most of resources are wasted). Caster should never nuke. Caster mana is for crowd control, mass protections, debuffs and killing gnolls. Ranged DPS should be dispersed away from healers, but within range if a spot heal is required (they should be mostly able to keep themselve up). Bard is designated to heal the main healers and caster. The shroud on elite should take 4-9 rounds to complete with this method depending upon DPS. Even if it goes 9 rounds only 1 or 2 pots should be required. If healers don't have empowered healing, they will use more pots.
Part 5: largely the same as 4, only the group should be in range of a pool so healers can use it while healing. Caster should Debuff with waves of exhaustion and cloudkill and cast protection from elements as nukes from Arratreikos go off. Be advised, blades will come out, so ranged should have healing on them and they are responsible for keeping themselves up on this part.
Happy Shrouding.