Yeah, for sure, I wasn't saying that the level design team be forbidden from doing their own concept art or sprites, just that it would be helpful if the art team was there to help them, and present more options for the concept art and sprites. Because perhaps one artist or level person does concept art that's great for an area, but another artist does a different take, then you don't want to shut out potential inspiration, and you can always create a synthesis of ideas.
Personally, I think the world as a whole needs to be explored more, the cultures fleshed out further, before any final mapping is done. Simply for the details. Until you know about the economy of the Hylians, how it's related to that of the other races, things like, do the Zora come into town and have a fish market, are Deku scrubs banned from the market from ripping people off, things like that, how can you create Hyrule town? If you don't know how the forest temple is/was used by the Deku, you can't really sprite it.
BUT, you can certainly create a rough draft that gives the layout, where the residential area is in relation to the market and the castle, or design a dungeon, its traps and rooms, but as far as specific things like, who will have a shop where, what will decorations be like, how will the walls of a dungeon look, etc, then those details will have to happen after the world is fleshed out more.
That's why I think the art team needs to get together.