An idea of what to expect. I will go with that. Entering a dungeon will do that for you. You can probably exit after the first boss. You don't even have to complete a boss. The thing with completing a dungeon, whether its a bronze/silver/gold, is that you are reliant on your fellow players. Take a healer who doesn't know what healing is and you will fail. It's more a measure of your fellow players than it is a measure of you. If you go with 4 good people you could be completely useless and still walk away with everything you need.
The only way you are going to tell if someone can raid is to do a couple of raids with them. Watch how they learn (some people don't) and keep an eye one their performance. An attunement is much like the achievement requirements for pugs that are floating around in another popular MMO.
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It shouldn't exist at all. Forget about being made shorter. Now that's out of the way, lets talk about the world bosses. What do they teach you? 1k people all AFK auto attacking. We will get onto the other things once this one is out of the way.