I don't think this is a "limitations" issue. I think they do it on purpose and I see it in many many MMORPGs. They tend to hide the DPS algorithms and how exactly stats work and affect DPS because they want to keep balance by hiding the "golden" formula so you can experiment and they can also hide any weaknesses in class and combat system. They also tend to change those algorithms from patch to patch without saying what exactly they changed. I think many devs fear the abuse will come by exposing the whole system to players. People will go to the golden classes and gears and exclude all the others. So they hide it. If you are to expose everything to the players you have to be sure everything is balanced and there is no perfect balance in any game.