[A reader suggests only Tyrion and Jaime appear to have a sense of humor.]
What, you don't think Dolorous Edd is funny?
I agree that humor has to be part of the mix. Even black humor, of the sort that policemen and fire fighters use, in part to distance themselves from the horrors they have to face daily on the job.
I think there's more humor in the books that you're seeing, however. But then again, "funny" is a most subjective thing.