As has been said before, humans lack a special ability for the ability to make use of damage techniques. In addition, they are also the highest ATP class to get access to A rank Crea weapons and they get a 2% bonus to all basic classes, a 3% bonus to all partial classes and Protranser, and a 5% bonus to the Acro- classes.

But, no, the bonuses do not make human any stronger than Cast or Beast, unless you're comparing a human male Acro's ATP to a Cast female (which is obviously a flawed comparison). Even then, that tiny advantage goes away when accuracy is taken into account. It does, however, balance the lack of a special ability and make the melee and ranged damage differences between Cast and human very small (on the order of a 3% output difference as partials and probably around 1% on the Acros).