Well, yeah, I think I read something similar at TvTropes the other day :| It's a complete overkill.
Deidara's explosion, while smaller, was said to cover a 10 km radius, which is about 10 times bigger than an average atomic bomb, or so. Not to mention it should have been instant, and the shock wave from it would have obliterated an enormous area around it, too. But instead it was a slow moving... shape?
Also, in one of the earlier instances Kakashi could teleport Deidara's exploding clone away with Kamui... After the explosion has already started. So obviously Kishi doesn't want to make explosions in the manga realistic - I don't recall ever seeing shock waves in Naruto.