Just wanted to add my thought to this as well. When you are dealing with a computer generated random drop rate, you really aren't completely random, because the program has to have some sort of logic to create the seeming randomness... unknown to us but known to the programmers.

Perhaps one of the factors it takes into account is how many of a given class were created server or game wide as opposed to present on a raid. Therefore, multiple u-nplayed or under level character's could be affecting the programmed drop rate.