In my personal experience I like playing mmorpg even if I spent most of it alone because the people make good backdrops lol (outside of raids I pretty much played WoW exclusively solo, even back when it was harder). FFXI didn't give you an option though lol, which was cool some days and very stressful other days (shouting for a few hours to find that you have to go now and spent all day doing nothing). I was absolutely fine with the GW NPC party system, also I would disagree that it died within a few months or that they didn't intend the solo content that way.
That said while I think it might lower the pool I think it will maybe only lower it by like a minute in wait time, so those who still want to play social can do so (I like DF social, easy to set up lol, I don't like waiting for PF haha). Also I imagine if you have a good group of friends you're going to be significantly faster in run times than an npc group.