I didn't say that it was just for defense, I said that he's getting paid for his offense AND defense. Run prevention is just as important as run production. He's getting paid for the whole package. He's a plus defensive third baseman, they don't hit the market often because they're hard to find. That's what made him such a prize get for this squad. His leg injuries have come while running the bases, if I recall correctly. So, DHing him doesn't solve that problem.
Filling the DH spot can be done effectively many ways, filling a defensive hole at 3B with a guy that can hit cannot.