Players have also been clamoring for a pre-patch as good as the WotLK one, so if the idea is that Blizzard is lazy because they copied something then I don't think the solution is to copy something else.
Besides, the Legion pre-patch was cool and all, but it was popular because it gave loads of experience at a time when levelling was at its worst, and secondly it gave loads of unique transmog, which players were incentivized to get before it was too late.
The first is obviously pointless considering you can level quickly anyways, and the second could still be something we have yet to see patched in.
Honestly the only think I really don't like about this one is that much fo the pre-patch will be happening in Icecrown instead of the capital cities, which I think is the true magic spice that makes or breaks pre-patches.
That being said I have yet to experience a pre-patch that isnt the most fun time to be online anyways, even WoD, so I doubt this will be the one.
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Even the books don't explain what happened really. We know they were hunting Sylvanas, but as for a quest that actually conclusively establishes a before and after for the kidnapping we are in the dark. So far it seems like we just log in and are told that they have been kidnapped already.