I’m staying out of the discussion with Pheandra since Zaltaan is covering it better than anything I could really add, but I did want to say that I agree with Zaltaan, and shared the opinion as well:
However
Gharion:
Hell, if you want to go back even further if Thrall wasnt a total coward and had brought the hammer down on the warsongs cairne could have been able to hook the orcs up with night elf allies in two years tops, never forcing them into the Alliance to begin with.
In larger context I also agree with this point, though:
The Night Elves should have always been on good terms with both the Alliance and the Horde. Even if the Night Elves joined the Alliance, the Horde should have seen the Night Elves as their allies. Warsong Gulch never should have been a battleground. The Horde never should have attacked the Night Elves. Not during Classic. Not during Cataclysm. The Night Elves should have never cut of trade after the Wrathgate. The Horde and the Night Elves should always have been on good terms. The War of the Thorns should have never been a thought the Horde would have allowed to pass through their minds.