At Least Learn To Fake It
Hal Curtis makes the point that art directors should know how to draw. In days past, this was a given. But you find more and more art directors these days who can't draw. Hal's point, and it's a good one, is that drawing is something that can be learned. It's not hard to do.
What I find, more and more, is that no matter how much we preach that it's about the idea, it's also about presentation. It's hard to convince anyone, especially a client, that a rad executional idea will be rad if it looks like crap on paper.
A super-talented art director I work with, Lance, has made somewhat of an artform out of compiling relevant images on a light box and then tracing them to build his comps. They're clear. They look professional. And they're not hard to do. If you're an art director who can't draw, and you don't have the time or inclination to learn, I highly recommend you at least get yourself a light box and learn to trace.
The drawing above is Lance. I traced it on a light box.