Or, considering that the government had a hand in framing Naofumi, and dismissed him on the sole basis he was the shield hero, everything they said could be totally full of shit.

The other three are all attackers, so one would think that the shield hero with no offensive abilities was meant to be a tank and generate all the aggro. Naofumi's defense is really high. He got gnawed on all day by the orange balloons and doesn't appear to be fazed at all. Normal folks freak out about those things biting the shit out of them.