I hear you. I'm in a similar situation...we have to have a product launched by mid-December, even though we don't yet have all necessary assets from the design team to complete the product. Their deadlines were moved, but the developers deadlines stayed the same. Bottom line...this kind of thing happens too frequently.
Your boss is probably an engineer. They give the design people lots of deference because they don't understand them or what they do, but ever since Apple they've been told that they're important.
A little knowledge is a dangerous thing.