Less math with some facts.
Any info used here was tested under RAWR v2.2.28 and general raid experience with the most of the gear from Heroic Trial of the Crusader 10, Trial of the Crusader 25, and Mjolnir Runestone from Ulduar.
Much as I'd like to run with all the theorycrafting I've found, there's only so much application that can be used. Yes, with best-in-slot gear and some experimentation, you could reach 10,000+ DPS in a standing fight. But standing fights are going the way of the dinosaur unless Blizzard runs out of ideas.
As the Marksman Hunter, it's up to you to conk out a godawfully high amount of DPS. But Marksmanship is dependent on your weapon's potential damage above all else. All skills here are presented at their maximum rank.
Kill Shot, and Steady Shot have been left out as these are used across all three specializations.
Ranged Attack Power = RAP Weapon Minimum-Maximum Damage = Min-Max
Arcane Shot = 0.15(RAP) + 492 Black Arrow = 0.1(RAP) + 2765 Chimera Shot = 1.25(Min-Max) + (2.8*AP/14) Explosive Shot = 0.14(RAP) + 386 to 0.14(RA) + 464 Multi-Shot or Aimed Shot = Min-Max + (RAP/14) + Ammo + Scope + 408 Serpent Sting = 0.2(RAP) + 1210 over 12 seconds
Beast Mastery counts on Multi-Shot and Arcane Shot and only Multi is reliant on the weapon damage, but not as a multiplier. Survival has Black Arrow, Explosive Shot, and Aimed Shot which takes the same formula as Multi-Shot but without the 0.5-second casting time.
Assume you have 4500 RAP across all specs, use the best ammo with 67.5 damage and have a Heartseeker Scope. Arcane Shot will give you 1167 Arcane damage, Black Arrow will give you 3215 maximum Shadow damage and Explosive Shot will give you a maximum of 3048 to 3282 Fire damage. Serpent Sting will deal a maximum of 2110 Nature damage.
Cut to Chimera and Aimed/Multi, which actually make use of your weapon. Let's say you have a Drakkari Hunting Bow which does 188-350 damage.
Chimera = 1.25(188-350) + (2.8*4500/14) = 1135 - 1337.5 + 844 Aimed = 188-350 + (4500/14) + 67.5 + 408 = 984 - 1146
Piddling, isn't it? Beast Mastery pets will do considerable damage and Survival's DoTs will outdo them.
Now let's use Siren's Cry instead.
Hit Rating needs to be at 263 minimum. That gives you and your pet an 8.02% chance to hit, guaranteeing a 100% hit rate on bosses unless they have dodge-boosting skills. You could achieve this with Focused Aim, but most gear can get you to the hit cap and leave few alternatives short of denying Rogues and Feral Druids their gear.
Agility comes next and should be boosted to whatever you can get it.
Armor Penetration follows, but getting the soft cap of 735 with the Mjolnir Runestone or 788 with Grim Toll is a pipe dream. Most fights aren't just tank and spank, so you won't get to use the procs effectively. We're going to lose this in Cataclysm, so make good use of it while you still can. That still shouldn't stop you from picking up either trinket while you wait for the two versions of Death's Choice or stuff from Icecrown Citadel like the Herkuml War Token, Deathbringer's Will, or Needle-Encrusted Scorpion.
Haste is by the bottom of the chain. Some of the newer trinkets support haste, but if you're stuck in moving fights, you can't make use of your light speed arrow/bullet chucking.
It goes without saying that you'll need the Flask of Endless Rage. Other Hunters swear by the Elixir of Major Agility and Elixir of Mighty Thoughts combo, but I haven't dug into that. When it comes to food, don't dive into the Fish Feast your fellow raiders put down. Chow on some Blackened Dragonfin for the 40 agility buff.
Just don't expect the auction house to be friendly if you have to buy your food.
The Delicate series of gems should fill up all of your red gem slots, with Wicked gems taking the yellow gem slots. When it comes to blue gem slots, use a Nightmare Tear for whichever gear piece provides you with the best boost to agility. Anything else gets a Delicate gem.
Talents and Glyphs
With another Hunter as support with Improved and Glyphed Hunter's Mark and Trueshot Aura, you have four free talent points and a glyph slot.
Glyph of Steady Shot and Glyph of Serpent Sting offered the highest output with the former having limited usefulness in a moving fight.
Aspect of the Hawk rates highest among the optional glyphs, but like Steady Shot, it requires standing fights for optimal usage.
Glyph of Trueshot Aura follows in damage output, then Kill Shot, then Rapid Fire.
Some talent builds are 11/53/7, favoring Aspect Mastery for the extra 90 AP in case of moving fights. Others are 7/57/7, selecting Barrage, Improved Barrage, Wild Quiver, and/or Improved Steady Shot for the extra damage. Personally, I'd go with 11/53/7 since Wild Quiver
Start off with Rapid Fire, Berserking/Blood Fury (if you have it), and Call of the Wild.
Serpent Sting, Kill Shot (when available), Silencing Shot + Aimed Shot, Chimera Shot, Steady Shot.
Depending on your haste rating, you can get 4-5 Steady Shots before both Aimed Shot is ready and Chimera Shot has 1-2 seconds left before it's ready. With Improved Steady Shot maxed out, you have 4-5 15% chances to power up your Aimed Shot.
Using Aspect of the Viper is all about judgment. With a thousand mana left, the boss at 10-15%, Rapid Fire cooling down and mana potions unusable, you might not have enough to sustain a few more rotations.
Under a good raid setup that can effectively burn the boss, go for just enough, which can range from 25-50% of your mana bar.
The Wolf reigns supreme above all other Ferocity pets with Furious Howl, boosting your attack power by 320 for 20 seconds every 40 seconds. And it's probably the closest thing to man's best friend. The Hyena's butt-ugly and the Cat only cares when it's feeding time.
Your pet contributes at least 500 points worth to your total DPS. Supplement this with 2 points in Cobra Strikes, 1 point in Great Stamina or Dash, 1 point in Bloodthirsty, 3 points in Spiked Collar, 3 points in Avoidance, 3 points in Spider's Bite, 1 point in Rabid, 1 point in Call of the Wild and 1 point in Wild Hunt.
Caring For Your Pet (and your DPS)
Before every encounter, check your pet's autocasts. There's a known bug caused by entering an instance that sets all pets' autocasts to active.
Know any boss skills that could kill your pet quickly. Though you'll have two points in Improved Revive Pet, you can't afford to spend that much time and mana resurrecting your pet, wasting multiple shots. If your pet is your best friend, Ctrl+2 is your pet's best friend.