To express my idea on the topic I have to rely on the information I can’t confirm / check, as the original source is not available.
First of all, I’d point out the original concepts of the blood elves. They were a lot more of a subversion of the usual ideas about the elves. Just like the original night elves supposedly to be “not just a yet another wood elves”, similarly blood elves supposed to take a different and darker turn, the one that would create a serious divide with the alliance and solidify their presence in the horde. For story enthusiasts more info could be found in:
But the follow up seems to be that the owners of the company, vivendy at the time, had a different idea on the topic. And a bunch of developers were fired. So, whatever was going on after the original assets for TBC were created, resulted in the slowly but surely shifting in the direction that started to be apparet in the next expansion, WotLK, but fully start to blossom in Cata.
A bit more wordy description:
Shortly after WOW had launched, the game had become a huge success, performing much better than Blizzard had anticipated. In the years leading up to launch, Blizzard had hired many new employees. Top executives now wanted to do a mass firing of these hires.
Kern was opposed to the firing, saying “we told them that we were like a family.” The team spent the last 2 years in crunch time and didn’t deserve to lose their jobs. He also didn’t believe that the firings were necessary because WOW was a huge financial success. Instead, he proposed normal performance reviews and firing only those hires who weren’t performing up to standards.
In a closed-door meeting of 4 or 5 top Blizzard executives, Kern was told that with WOW’s success “we’re a real business now.” Kern says this was the moment when “big corporate gaming” thinking similar to Electronic Arts began to take over at Blizzard. He quit shortly thereafter. Blizzard went ahead with the firings and they were hugely unpopular and damaging to team morale.
Although, I am unable to find the actual interview with M. Kern to confirm or deny any of the claims, so, here is the source I used:
https://www.reddit.com/r/Blizzard/comments/9z1y57/mark_kern_lead_developer_on_wow_tells_the_story/
Whether or not it’s correct about the events unfolding shortly after the release of WoW, I can’t tell.
But it seems like that would fit. If indeed they cut the development after the basics were implemented, that would have affect of the story and execution. TBC stuff was mostly clear, WotLK was a mix, and later - we know what happened later.
Plus, likely Metzen and other original creators had to work on a bunch of other projects other than refining and iterating WoW, which did not really help. And could be a reason for gradual shift from what supposed to be there, to a mix of bits we have after.
gl hf