Except you get to kick ass of Arthas himself
Only difference would be trivial - you control one character or platoon.
In WoW you don't play as some random foot soldier. You go on and kick ass of Kel Thuzad and like, obvious core characters and enemies of the setting just like in RPG. Only difference is there are millions others doing the same thing.
MMO players don't want to have nothing IMPORTANT to do. In Guild Wars your actions and importance is just as vast as in single player RPG. same with WoW. Your ragtag bunch of players does all the same stuff your hero and NPC party would.
As I said difference would only be trivial. And Battleground system or whatever it is called is quite advanced. I'm not sure if it lets you to command AI characters fighting but YOU and your FRIENDS are the key of quests, shaping the world, saving plot critical characters (like millions of others), investigating strange ruins (like millions of others), kicking bad mofos asses (like millions of others) etc.
ONLY difference is that in MMO it all is utterly meaningless. But that doesn't change core nature of game's important missions.
Besides, the Battlegrounds system (based on which you refer MMO characters as foot soldiers) is not integral to main storyline quests and raids which players are doing all the time.
No, WoW retconned whole Warcraft mythos and added bazillions of new stuff. And you don't play as mere "foot soldier" if you don't want to, you get to change the whole world, defeating slumbering Ancient Gods (stolen from Lovecraft btw) rising from depths of earth... untill mission resets to next party that is.
again you're confusing battleground skirmishes and small time missions with BIG storyline quests and raids that are ever present in MMO's. Especially in games like LotR Online and Guild Wars difference in main character's importance (in comparison to single player PC) is near to null.
You save the world in MMO's too. It is completely meaningless but you do it.
You really think MMO players would be happy with merely standing by and not doing anything important?
I find this whole deal with you guys trying to squeeze out the hellhole kotor has fallen in rather humorous as your misconceptions about MMO story and quest structures