Players of other games have often voiced dissatisfaction with developers for artificial delays when they seem excessive, or as a method to "hide" the fact that content is unfinished. I don't think a week or two of delay is unreasonable.

Since someone else brought it up: Blizzard has staggered raid unlocks since Mists of Pandaria's release, wherein the first normal raid was unlocked about 10 days after the expansion's release. For Warlords of Draenor, the first normal/medium-difficulty raid was unlocked roughly two and a half weeks after the expansion's release.

Personally, if I'm going to set aside time for the raid content, I'd rather only do that once -- for the actual raid content -- and be able to level jobs, do quests, etc., at my own pace.

For other players, being given more time before the raid unlocks means they have more time to play the new jobs, get comfortable with new gameplay, and generally stretch their legs in the expansion before settling into static groups.