And this is where you're wrong, and apparently it's a bad thing to point out the fact that based on the response alone, here and on other forums, with the exception of a handful of 'Northeron' types, the Void Elves are giving alliance fans the simple pleasure of an Alliance Blood Elf. It's the *exact same model* Different skin tones and different hair options are about it. The skin tones basically resemble night elf tones. I've been dealing with elf crap for a long time now, trust me when I say this is going to be a massive fan service for a lot of people who want the following.
1) a 'high elf' that is basically an Alliance belf, no specifics needed for their itch to be scratched
2) a 'blood elf looking night elf' so they can screw around pretending they are a highborne or something
3) an edgy, brooding 'dark race' on the Alliance
4) simply want the aesthetics of a blood elf but on a faction their guild/friends are mostly on.
The fact they are putting Alleria in charge of this 'race' is another fan service for these diehard Alliance players who think Alleria and Turalyon should be relevant to WoW. There is no serious development for them. The 'question of numbers' to constitute a race is out the window. But I bet this race will be exceedingly popular to the point where you can honestly see void elves vs blood elves being norm in battlegrounds.
Zandalari trolls are the fan service to the Horde however unlike the void elves, they have a firm root in the lore. Horde players would expect nothing less. Alliance players do not care as much. Something else that can be gleaned by the fact the Horde story is always the melody in wow and the harmony is the alliance.