I dont get why people think senior game designers are the ultimate creative source. I read an article about GZ (Geoffry Zatkin, the original EQ spell guy coincidentally) a while ago and he was basically saying that the designer job was more like a project manager not an idea guy. He moved on to Monolith Productions: Matrix Online, Aliens vs Predator, few other ok games, long ago.
I'm not sure if it's just SOE or the industry, because from Tigole's feedback on WoW game design it sounds like he's got a big part in the creative process. Maybe hes just communicating his meeting stuff though.
Heres that article, yeah its like a year old but its relevant to this discussion I guess. It's on Smeds favorite gaming site too.
http://www.penny-arcade.com/2005/04/04