The passive miss chance for thieves and mages is chance *= 1.0; but for some reason a mage/thief receives chance *= 0.8; that seems like an oversight, since mages/thieves really shouldn't have a worse miss chance than either class when they both have the highest miss chances.

Correct me if I'm wrong, I'm not much of a programmer.

The other thing in the code that caught my attention was the whole no parry until lvl 7. Has it been removed, or was it never active?
// if(level < 7)
// return(false);

That's the miss chance modifier. That means if your base miss chance is 10%, then chance * 1.0 = 10%, whereas chance *0.8 = 8%. It's better to miss less.