The thing with dual spec is that it initially was meant to be for people to have one for pvp, one for pve. Then, they went and switched up raids so that every encounter would need differing amounts of tanks and healers and dps - basically forcing any decent raider into dual speccing PvE roles.

"there has to be a line drawn somewhere and that line should be to make one talent tree essentially for pvp."

Blizz can't do that with their current specialization system because there is no way, with just 3 trees, to keep all they hybrids in all their roles in PvE if they made one a "pvp only" tree. Shaman, druids, ret pallies, priests, death knights, warriors would all be up in arms about it.

There are other MMO's that have a "PvP only" spec, and those trees have things like "Increases damage against player characters by 15%." I think a better option for blizzard would be to add an entire line to each tree in the game that was an "against player character" type line of talents, OR, create a 4th spec for each class that would not be allowed to be a primary spec, but would be filled with "against player character" talents.

This would also make pvp much easier to balance, because then blizz could balance those pvp talents without touching the pve talents of the other trees.