How would the story be if the Night Elves were in Horde in the first place?

[Razion]

Overall a great read, but one thing doesn't really make sense to me. How does the Night Elves joining the Orcs influence the Scourge taking over Lordaeron? As far as I know, neither orcs nor night elves did anything on Lordaeron. Arthas was pushed out of Lordaeron by Sylvanas and the forsaken and they were helped by Garithos and the remaining humans. Tyrande, Malfurion and Maiev came some time after that in the pursuit of Illidan?

Archived Page, Scourge Invasion (patch 1.11) event:

[...]The city guard will need all the help they can get once the Scourge unleashes its wrath on the cities. The Argent Dawn has already heeded their desperate call for help, setting up camps inside the besieged cities and rallying the defense against the encroaching darkness.

For the purposes of evaluating the defenses of Undercity during this event, we can take the lines that needing all the help that they can get, and a desperate call for aid from an already Argent Dawn assisted Undercity means that the combined forces of the Undercity and Argent Dawn, by themselves, were not sufficient to defend against the forces of the Scourge during a Scourge Invasion. So, without the Horde, any and all corpses in the northern half of the Eastern Kingdoms would likely be forfeit to the Scourge. As Stormwind shares the same description, this means that with the Scourge bolstered by the northern half of the Eastern Kingdoms of any and all corpses therein, the Scourge would wash over the southern half of the Eastern Kingdoms as decisively. Even if we were to assume the Forsaken and Argent Dawn could scrape by one Scourge Invasion, could they survive the second? As Undercity and Stormwind barely held off with the Argent Dawn even with the Horde's help for both of these events, together weaker not only from the loss of the Horde, but also potentially facing an even greater threat if the other falls, I think we can assume that after two Scourge Invasions that the Eastern Kingdoms would decisively be run over.

[Soon-TM]

I mean, if belfs could overcome their long time dislike towards trolls to rally under the same flag (sure they were not Amani, but I very much doubt they would have cared a lot), why not. If anything, nelfs in the horde would make a lot more sense than belfs do, when you think about it.

[Eggroll]

I meant in the first place like starting from Classic. Also since the Night Elves sabotaging Ghostlands were under the Horde, the Blood Elves would most likely be Alliance again

Hmm, starting from Classic? Well, then the orcs would have had settled somewhere else than in the sacred nelven forests because I can't see the nelves standing by twiddling their thumbs while orc peons are chopping up their precious sacred forests.

What I will say is that the Horde would probably have made for better allies IF the nelves were on the Horde because clearly the Horde would never have given the Alliance a pass for a thing like Teldrassil - like the Alliance did, or not defend their own and let them die in cold blood like Anduin did.