In this context, the term “meta” is shorthand for “metagame”.
http://en.wikipedia.org/wiki/Metagaming
“In simple terms, it is the use of out-of-game information or resources to affect one’s in-game decisions.”
The term Metagame is used in several contexts. These are usually competitive in nature. For example, let’s pretend I play a game of chess against an opponent, and I know that they have a particular strategy they often like to use whenever they play. I may try to use my foreknowledge of that person’s strategy when I play against that particular opponent.
Another example would be picking and counter-picking in game formats where this is allowed. For example, in a MOBA, teams alternate in their choice of picks. Let’s say you’re on such a team, and the last player to pick, and you had some particular hero/champion that you wanted to play. However, you look at the other picks of your opponents’ team, and decide to play with a different hero/champion, knowing that your new choice counters the choices your opponents made. This is Metagaming at its core. You are using your knowledge of the matchups of various heroes/champions to decide what your next move should be, rather than simply picking your favorite hero/champion every time.
We can apply this concept, too, to games where many decisions are made beforehand. Take Magic: The Gathering. Let’s say I want to enter some tournament. A good strategy to start with, when choosing to enter an MTG tournament, is to go look up the “metagame” of that format (let’s pick Standard). I go look up the Standard Metagame of MTG, which means I look at the most popular decks for the Standard Format in Magic. This data of the most popular decks is called Magic’s “Metagame”. So I look at these decks, notice that many of them play a particular strategy, so I go ahead and build my deck to counter the choices of what is popular. Mind you, an even better Magic player will realize that other players are doing this exact same thing, and so they will attempt to go further, and try to counter the choices of the people who are trying to counter the Metagame as well! And so on.
So the question becomes, how on earth does this apply to a non-competitive thing like GW2 PvE? Honestly, it has to do with Guild Wars’ history. In Guild Wars 1, much of the harder content could not be done without specialized builds. This was because GW1 had highly creative and fine-tuned encounters, and players’ builds could also be highly tuned, complex, and creative. The content in high-end PvE in GW1 could be so difficult that it required that players research and theorycraft builds, just to overcome it. This is an example of Metagaming in a PvE enviornment.
Once GW2 came out, it actually turned out that no such content exists in PvE.
>_>
HOWEVER, much of the try-hard spirit of GW1 players remains, and so a mantra was largely started that one could not simply do a dungeon, they had to do the dungeon efficiently. And there is actually something to this. If you’ve done a dungeon path multiple times, you will soon grow weary of taking 30 minutes+ to do a single dungeon path, when you know that an efficient group can do it in 20, 15, 10, or even 5ish minutes. In fact, since GW2 has had the same dungeons now for over 2 years, many of the veteran players simply get bored running dungeons in an ‘inefficient’ manner. Therefore, what started out as the mantra of a few “elite” players gradually grew to become the widely-held belief of the general player base. Many players who still run dungeons don’t care to do them inefficiently, and want players to run the highest-damage, most efficient builds possible. This is how we ended up with a “Metagame” for a game that does not have truly challenging PvE content. Enjoyable but unchanging dungeon content over two years caused adjusted the community’s expectations to have “speedrunning” builds as the so-called “Meta”.
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I am familiar with this site and Brazil’s ranger builds. But I’ve never seen numbers for condi Rangers earnestly run by him or other players.