Because DPS is the primary role of 3 classes. Why should a warriors secondary role be on par with other classes primary role? If this happens what will make people choose to make a ranger alt? Warriors level faster, and at least on my server are much cheaper and easier to gear. Why would someone choose to make a ranger alt if they can achieve the same level of DPS (your "dps balance") more cheaply and with greater survivability?All classes will always be needed. Mages for lures, rangers for bolas, druids for heals, warriors for tanking and mages for luring/freeze. Since this is the case i don't see how creating dps balance would at all eliminate roles of classes.Dpsing is a role in and of itself, putting every class on an even tilt destroys dpsing as a specialized role and eliminates the need for certain classes. I personally dont think that eliminating the role of multiple classes in order to cater to another is creating balance.5 classes is barely any lol. Agreed every classes have roles but they should also be able to go against roles for dps. Why should there be any dps warrior skills if they are purely for tank and why introduce DG?
I also want to point out that tank warrior is a whole build, with much greater depth than say support ranger. Most of a rangers support skills are useless and need fixes, and really the two viable ones, bolas and entangle are usually carried by full DPS rangers as a backup skills. Therefore there really isn't such a thing as a "support ranger," and therefore we really only have 1 role.
Because of this, the dps distinction between ranger and warrior is important since it's really the only advantage/reason to choose ranger over warrior that we have, sadly.