I am not sure the designers names on the cover are a really selling point to most gamers. Or, perhaps more accurately - the sort of gamers who can tell one designer form another are also not going to be deterred by not knowing the name on the cover.
I'm sure you are right, but I'm not sure that it follows that even if the consumer does not know the name that they aren't able to distinguish between the quality of the product. In short, I'm saying that some designers really produce a better quality product than others, and that those designers will establish a reputation eventually.
As an example, when it first came out I became a big fan of Babylon 5. Because this was now the 'internet age' it was possible for us fan boys to track the show more closely than ever, and so I learned the name J. Michael Straczynski. So I became a fan of JMS. But then what I learned is that I had literally been a fan of JMS for years before. I was HUGE fan of 'Captain Power and the Soldiers of the Future' and I owned the toys. I watched 'The Real Ghostbusters' every afternoon after school. I was a huge fan even though I had never noted his name.
Likewise, during college I became a fan of David Gerrold through exposure to the 'War against the Chtorr' series, but then discovered that I hadn't just become a fan - I'd always been one my entire conscious life. I'd been a fan of 'The Land of the Lost' back in pre-school. He'd wrote the 'Trouble with Tribbles' episode for Star Trek. In short, even though I'd never made an attempt to follow him by name, I'd managed to do so.
With RPG writers, my first experience of this was with Tracy Hickman.
Just because we live in a culture that celebrates brands and not artists/producers, doesn't mean that brands survive independently of the artists/producers that create them.
The ideal situation for an entertainment brand like 'Dungeons and Dragons' is that they have a healthy relationship with an artist from which they buy the rights to intellectual property that becomes the selling point of the brand.
Stan Lee created comic book characters. Stan Lee is a selling point for Marvel. But Stan Lee also created intellectual property for Marvel which will continue to be a revenue stream for the company long after Stan has gone to the great creative team in the sky. Stan may leave, and this may be a blow to the company, but as long as the company retains Spider Man, Iron Man, The Hulk, X-Men, etc. they are going to retain a fan base and be able to market a product.
Just to provoke some conversation, how much new IP of this sort has WotC created in the last 10 or 12 years? Doesn't it seem to you that they are _still_ mining the IP of decades past? How much of what they've done since the 25th anniversay is simply just revisiting again and again what they made in the first 25 years?