The class is frightfully boring. The most recent iterations have made some improvements but I personally don't feel it's enough to justify the switch unless the class is given raw power.
The idea, and this is an old argument, that we needed another melee spec in a game where sometimes three to four or less melee are brought is rather foolish. If you're a long-term ranged DPS in a raiding guild why would you switch to a role that most likely would see drastically less raid time? We have yet to add a ranged DPS spec to this game since its inception. The closest we've come is a Mistweaver and even they are A) not DPS b) melee-ish. Demon Hunters could have had a ranged spec. Lore would allow for it and even if it didn't, it could have. It's a game. Give us an interesting story and include it. The class literally only has two specs. It's beyond dull.
As so many specs change, people are seeing variety inside their own classes that I could imagine diminish the 'newness factor' of Demon Hunters. While I'm personally terribly disappointed in the MOBA style approach of stripping abilities away in the game so one ability bar can handle the entirety of a class, I can see how class revamps give something new to look forward to a current class.
Even if the game comes out in 3-4 months, it shouldn't. The game is not there yet on Alpha. There are still poorly implemented changes and the game still has its string of bugs. Combine that with the only really specific group that has alpha access is 13/13M players who maybe are a tad burned out by farm and content drought. It's entirely possible to have a bunch of people who aren't really invested in Alpha so their motivations for contribution to the discussion of a class that is boring, reduces their raid time, and doesn't even compete with their current class might prove to be a tad bit low.