I always assumed the draenei starting zone takes place before the blood elf one. The timeline fits a lot better, since the status quo in Quel'Thalas seems to have been quite some time (months, probably) after Kael'thas took over TK, kicked the draenei out and shipped M'uru back home. On the other hand, the draenei crash land their ship and you start off fresh from the wreckage, scrambling to find survivors.
The draenei form a bond with the night elves after their starting zone, so chances are they informed them about what they saw Kael's lackeys doing: palling around with demons. Hence the Sentinel squad going in to see what the blood elves in QT were up to, since at that point there wasn't a public distinction between the blood elves on Azeroth and Kael's dealings with the Legion.
Honestly, I always found it weird that Gobbos are horde only. Back in WC III everyone could hire them for cash. ._.
Worgen are o.k. though. They can stay.
Quel'dorei as a playable alliance race would be awesome. The only fact I hate about the Sin'dorei is that they are Horde... but i highly doubt that'll ever happen. Blizzard gave the Sin'dorei as a pretty race to the horde for a reason.Maybe when the next expansion really is about the Legion and there's Turalyon and Alleria and their son Arator we might see some High Elves as an Alliance race.
the high/blood elves hated the night elves already so whether they were "allies" with the night elves they would probably expect to come to blows with them.
however the dwarves and humans used to have good relations with the high/blood elves and the dwarf working with the night elves to help invade quel'thalas probably made the blood elves feel like "they chose them over us"
"I was a normal baby for 30 seconds, then ninjas stole my mamma" - Deadpool
"so what do we do?" "well jack, you stand there and say 'gee rocket raccoon I'm so glad you brought that Unfeasibly large cannon with you..' and i go like this BRAKKA BRAKKA BRAKKA" - Rocket Raccoon
But just to throw this in, I've just heard in an old tradechat video, that Night Elves were at one point supposed to be on the Horde side, but they decided against it because they saw more potential for conflicts if they were part of the Alliance.