I think thats where you might be wrong. He's been as effective as any forwards on the Habs defensively, theres a reason why Julien loves him. Julien, the guy who hates all youngsters, went out of his way to call him a "future" Bergeron.
Im not sure the comment you made is actually warranted or motivated by viewings but rather by some pre-conceived opinion that a skilled player cannot be good defensively, or that the less skill a player has, the better he should be defensively. Suzuki blows Thomas out of the water IQ wise and skill wise.