The immorts tend to not publish information to that much detail, preferring we work it out for ourselves. The thief multiplier is pretty well known because it's been that way for 8 years or whatever. The warrior bonus is new, and they haven't really said how much the bonus is, we just know there is a progressive bonus. The same is true of monks. The open hand damage does increase, but we don't know when or by how much.
Different bonuses are treated differently, depending on where they appear in your class order. For thieves, there is an additional multiple if you are thief prime (and some other added bonuses too), but thief 2nd, 3rd and 4th all stab the same. For warriors, I think the only bonus is if you are a warrior prime. For monks, I believe it gets progressively worse the further the class is in your classo.