Tobold ponders the directions of WoW and Rift. WoW, he says, is pushing raiding towards high selectivity based on gear and/or skill (I find the former more annoying in a game). Rift, he says, merrily invites everyone by having easier content and not limiting numbers. Players, he suggests, seem to be preferring the latter; I might append that vocal players of Rift seem to be expressing that preference, while subscriber numbers make it premature to ponder anything as a WoW-killer.
The day before, a LotRO developer diary lovingly described the design philosophy behind the new raid: higher difficulty, perfect execution, learning via wiping repeatedly. It explicitly contrasts skirmish Tier II (higher numbers) with the new raid Tier II (different abilities), although I might again append that I would be surprised if higher numbers (i.e. gear dependency) were not a factor.
My long-running game was City of Heroes, so I enter with an expectation that you can bring a full group of almost anything and beat almost anything. A few fights all but demand something from a small set of options, but those are notable because they are rare rather than the norm. Add to this the City of Heroes assumption that you will be able to play with your friends now rather than waiting two months for them to hit the level cap, and you have a very different philosophy than gear-gated tiers of raids.
I refer back to Tobold’s excellent discussion: does this encounter test the worst, best, or average player? The most restrictive content will test the worst player. Raids demanding synchronized dance and perfect execution wipe if you add one new or slightly undergeared guy. (See Spinks on the different effects of this philosophy in single- and multi-player games, or try a LotRO PUG Durchest raid in which one of your three tanks is not geared above the boss’s potential one-shot damage range.) Not restricting encounters by player count gives you a fourth option: testing the sum, so you can beat the Rift by bringing more people. Combining unrestricted attendance with testing the worst player would be apocalyptically horrible.
I cannot tell you what the mass market wants, because I am obviously an outlier, but I will favor a design that makes it easier to join with my friends, all of them, whatever level they are. Lowering the minimum difficulty threshold tends to do that.