I think you’re confusing dark comedy with satire (which is often, but not always, dark humored). A dark comedy doesn’t always have to be dry and deadpan; it can have broadly comic laugh-out-loud moments as well. Dr. Strangelove, which was mentioned earlier in this thread as archetypal dark comedy has numerous goofy scenes like George C. Scott’s impersonating a B-52 and the title character’s constant battling with his arm.
While No Country for Old Men has some darkly comic moments, I wouldn’t call it a dark comedy. It’s by far the most serious movie the Coens have ever done.
As for other dark comedies, I think Get Shorty could be categorized as one (but others may disagree).
It’s been so long since I’ve read it or seen it, I don’t remember. But another general rule of thumb is, if several main characters die for really stupid reasons, then it’s a black comedy.