I think the Warriors of Darkness storyline was a bit rushed, but mostly because it might have to do with the two goals this patch would have for the expansion story as a whole: Eliminate any major loose ends in the current expansion storyline and confirm general direction for where the next expansion is headed. By achieving both of those goals (more or less), this allows the MSQ in 3.5 to set up the complete stage for the 4.x storyline.
Yes, it was hasty, but I think the writers did the best that could be done given the goals required and what circumstances were or might have been involved.