You are taking a small number of gaming mechanics and talking about mixing them up, but you're neglecting the context in which they exist.CantFaketheFunk said:I think you're all missing the point here. The point is that it would still be a challenge, just an infinitely more scalable one.
Do the zombies lie down and die in L4D just because the Director adapts the game to how you're performing? Of course not.
Every L4D game starts the players at the roughly same power level, be it their first game ever or if they are hardened veterans. Furthermore, the are no lasting rewards for success.
WoW (and MMOs in general) do have a system of persistent rewards through which the players gradually grow in power (namely gear). Providing a dynamically scaling difficulty would also require dynamically scaled loot, otherwise people would simply exploit the system by sucking on purpose to get by easier. And if you made such a system, a group might win the boss fight only to get the "crappy" version of the items and feel like the game is telling them "You suck, but here's a little something anyway."
Also, you compare an FPS to an MMORPG. Let's try another comparison - Oblivion. Ask the general public how they felt about scaling there. Or better yet, just search these forums. The general consensus was that it was one of the worst features of the game. I'm inclined to belive that when it comes to the underlying game mechanics, WoW has more in common with Oblivion than with L4D.
And finally, WoW already has scaling. I haven't played in a while (quit just before WotLK) but as far as I know every Dungeon/Raid has a Normal and Hard mode.