As the same as just about anybody I had that same reaction, like wtf is this. After some hard thought I am currently starting to want this to happen. And, yeah sure, it wouldn't be an ideal situation for everyone and many will moan and whine. That is to be expected, but from my exp in mmo's (raiding since 99 in eq1) this has some chances to make it really good. This xpac is kinda a controversial one, it is making a good deal of changes, and if this was to pass as a fallback could be beneficial to the player most noted the raider.
Again not having everything is not the most ideal setting for a release. In our current situation of the game though to do this is a good option. The really focused raider will complain because he or she won't have the raids immediately.That same person would take all that time prepping for when they become open, so that they can hit the gates running as hard as they can. But they still would play it at the first chance to get in. A big lure at the beginning is always the initial push to the end as fast and hard as possible.
A slight delay wouldn't take away from this feeling as hard as people are passing it off as. In fact this could actually improve the raid experience for us, if you really think about it. And remember us as the raiding community is actually the minority; there are a bunch of new shiny things to touch. Sure, not everyone is going to want to play with them right away; some of us will want to spend every moment trying to gear up as much as we can. If this would happen, this kinda becomes a way to gate the raiding, if it was delayed 2-4 weeks at most the encounters wouldn't get the over-tuned feeling that most get in the first tier of an xpac. No later than 4 though, as that would just feel like a slap in the face.
Everyone still can be on the same page but when the gate is open the ones who really put the effort in will fly forward and others not so much. This would make that initial rush to world/server first even more exciting too. When that light turns green the games can begin.
This does come with some drawbacks though such as the pvp season. When will that start? Right away or when the raids launched? If it was right away that could feel like the raider would be forced to pvp more. The need to pursue this isn't as great, but still feasible since they are making some changes to the pvp/pve gear situation too. Which isn't a bad thing, and that would also keep raid gear out the early pvp. We all know that there tends to always be some kind of OP pve item that gets heavy use in pvp. *cough* Vial of shadows.
On the other hand, if delayed that would make the pvpers suffer too, and sure there are some overlap between them and raiders. Many of us pvp often as well, and having to wait for both legs of the monster would suck bad. Doing this would reduce the amount of arena gear in early raiding, but honestly at this point it matters little. Certain pvp items are occasionally better than some early pve gear and if done properly can do the job needed whether people realize this or not. Other than that, just waiting a brief period to allow people to get 90 so it is gated a bit are the only reasons I see them waiting. Even then I do not think that outweighs just starting it from the get go.
There may be some media backlash they would face for releasing game without the raids, but who cares as a player if someone rags over a choice like this. Honestly I would rather have the game and wait a bit in mop before I raid. As opposed to waiting to play mop until raids come out, because lets face it DS just doesn't cut it. I've not even stepped foot in ds since 15%, progression was done, and nothing to do other than stand on my fence post in valley of honor chatting. Them going this route may actually keep a larger player than waiting as well. The longer we are only left to farm ds the more chances they have of losing more players. More will stay if they are somewhat happy and waiting than hating what is still there and waiting.
For the next batch of clones, under NO circumstance, do you tell them they are adopted. Lesson learned - July 2007.