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According to this interview: http://www.zam.com/story.html?story=32077
"Raids" or whatever they decide to call it will be in at some point through adventure zones. Just not at launch. Some instanced, some not. And from the article it all seems highly subject to change.
A post on the temp-official forums follows up on this. It seems there will be large group encounters, just not like your typical 20 people vs overly giant sized mob
My personal opinion is they haven't officially decide how they want to do end game raids and everyone is way over reacting and theyre will be progressive content for guilds and such either at launch or sometime after.