The shorter the fight, the easier it is to get big numbers. If the fight is only 30s long you can pop death wish and recklessness right away and have them up for most of the fight. If half your raid is slacking, fights will be longer and it's hard to get massive DPS averages.
If you are going for absolute max damage there are also a ton of world buffs and harder to obtain consumables that you can stack on.
http://db.vanillagaming.org/?spell=15366http://db.vanillagaming.org/?item=8410If your guild is very good about debuff management you can also really optimize DPS by making sure that only the best debuffs are up. Armor reduction effects are a huge increase for melee and many of them stack. Sunder armor, Faerie Fire, Curse of Recklessness, weapon procs,
Crystal yield (not sure if this one stacks with the rest).
If a guild decides to stack debuffs for max melee DPS, you can get much bigger numbers than if you aim for optimal overall raid DPS.
I don't know how many of the above are being used by top DPS warriors on realm players and there are certainly other less-common buffs/consumables.
At that level of DPS tank threat is a really big part of getting consistently high DPS. Your tank needs to have both gear and a spec based on maximum threat.
So... I guess the short answer is, it's a group effort. You need the entire raid going for max DPS really.