Overshadow does not have to mean deus ex machina or DMPCs; I think that's poor DMing. It's also "overshadowing" (heh) this debate.
I never bought the "concerns of the might" stuff. Many of the high-ranking NPCs don't seem to have much responsibility, and are free to go adventuring. Even guys like Khelben (a lord of the a city) is one of many lords. Other lords can go away and do stuff, so what's his excuse? Given that, in the novels, Khadgar can tell you when a single drow is trying to sneak into his city, it's hard to believe he can overlook things that are actually big and important.
I'm probably going to be flamed for this, but I think World of Warcraft does a better job in this area. I don't play that game, by the way, but am interested in Warcraft lore and try to stay on top of it. In WoW, there are big name movers and shakers, and they're more visible than Elminster ever was... in a good way. King Varian can't help, he's leading an army against the Scourge in Northrend (or whereever he is) that's being led by the Big Bad (the Lich King). Khadgar can't help, he's busy organizing a massive force against whatever-the-heck is coming out of Ulduar. Lower-ranking movers and shakers are often visibly involved in long-lasting operations against foes suited to their level/rank/whatever, putting them out of the picture without having to say "she's getting her hair done". And this from a setting which is (rightly, IMO) criticized for having shallow lore in various categories. WoW provides so many quests that it's easy to see the movers and shakers simply do not have the time to handle these problems. The movers and shakers are also more "human"; if Varian tells you he can't solve a problem, that's easy to believe. If Khelben tells you the same thing, it's a massive dissonance from his hyper-intelligent persona in the novels where he's got an incredibly sophisticated spy network and has the (never-to-be-seen-by-players) skills to do things like move elven magical gates.
Maybe the big reason Eberron hasn't suffered from this problem isn't the lack of high-level good NPCs, maybe it's because their NPCs are believable flawed. Or maybe it's a bit of both. I dunno.
Speaking of which, many of the movers-and-shakers of FR do not inflict this problem. I can picture a bad DM having Drizzt hog the spotlight, but Drizzt simply can't be used as a one-button-humanoid-problem-solver based on either his abilities in the novels or his game stats. He can't teleport, and while intelligent, isn't an unrealistic (or extremely rare) genius.