No, this was perfectly written. Thor's base strength is beyond Hulks. He is physically stronger. Thor holds back when fighting the hulk, even physically, because he can die. As Hulk's strength grows in this lock up, yet Thor doesn't budge? He is generally applying more strength, which means Thor holds back. He's said it himself. Thor never uses full power when fighting the The Hulk, Thor has beaten a stuffed Galactus, Glory, The Surfer, Thor never uses full potential when fighting the Hulk. Why? Because their rivalry is very popular, wouldn't do Marvel any good to have Thor destroy the Hulk everytime, like he should. Thor holds back