I love FFXIV and all, but its approach to storytelling is VASTLY different than WoW's Because of that, I think treating the player as a "Champion" or "Hero" of their given faction can often times feel very frustrating.
Now, when I say "players should be treated as Adventurers", what I really mean is that we should be treated as random mercenaries. That's not to say main characters dislike us or anything, but our involvement in our factions should be something that is largely left to our own devices. If I am a Dwarf, it might be IMPLIED that I serve Ironforge and by extension the Alliance (thus justifying the opposing faction treating you with hostility), as an "Adventurer", you would function largely outside of it. You are not a soldier, you did not sign-up for the army, you are an adventurer whose goals are your own to define.
This serves two purposes:
First, it makes it more believable that NPC's of the "opposing faction" would be willing to work with you. If the President of the US launched a nuke at China, then it is unlikely a Chinese General would be willing to work with an American General. However, some random American bounty-hunter or something? Possibly. Case in point; it wouldn't make sense of Tyrande to work with a "Champion of the Horde" who could've prevented the burning of Teldrassil. Some random mercenary who couldn't have stopped it even if he wanted? Far more plausible.
Second, it gives Blizzard the freedom to make more bold decisions on behalf of the factions at play. Sylvanas burning Teldrassil pissed a lot of Horde players off, too because as Warchief of the Horde, they were also culpable for her actions. As Adventurers who were simply "paid to be there, in case they were needed", players would have the freedom to condemn Sylvanas, without feeling like there characters are obliged to follow her blindly.
It may seem a minor point to stress, but I truly think this distinction between "Champion" and "Adventurer" would just really absolve a lot of the ongoing issues with WoW's storytelling, and how it often affects players and their characters.