No. That is a lazy man's excuse for bad PvP balance. There are plenty of methods to enhance classes that are bad at PvP but already competitive at PvE. The most egregious (one full YEAR) case of BW leaving a class worthless in PvP is Merc dps. And yes, Merc dps is fine for PvE. But BW has gone out of its way to nerf PvP traits for Merc dps (i.e. Sweltering Heat). You can not explain this by simply waving your hands in the air and exclaiming that there are too many variables to account for. BW could easily buff underpowered PvP dps classes by adding a +10% resistance to damage when stunned or cc'ed to the top tier talent for these classes. This would have virtually no effect on endgame PvE.
The problem is far deeper than an inability to accounting for multiple variables. The problem is that BW has improperly diagnosed which subclasses need buffs and which subclasses need nerfs in PvP. The ludicrous buffing of Rage/Focus dps in 1.6 is just one example. Until BW catches up with the knowledge base that exists amongst the top PvP players, PvP balance will always be lacking. And the refrain of "there are too many variables, so I can't fix it" will always be weakly offered as an excuse.
*clap clap clap* give this man a round of appluse we have a guy with a brain on this forum and has hit it right on the head.
But it's more then that BW have been doing this since they first started making games there have been inbalances in all of there games.
here are a few i can think of off they top of my head.
#1 DA1: this game was so faving the mages that it's not funny have a mage on your team and the enemy may as well just kill themselfs since they are not getting close to you, having a team of mages well yeah thats just insta win since NOTHING will be able to get to your guys as long as you have alistar on your team as a tank and should he be hit with friendly fire have no fear just have one of your mages heal him with there super op healing spells.
#2 DA2: do i even need to say it mage again only this time they game the mages freaking rapid fire from there staffs pritty much the same as the first one just have a mage as a main and have them roll speirt healer and never worry about bandages for your team ever again just spend all that extra money on upgrades and compaion mods and insta win it.
#3 KotoR 1 & 2: do i even need to say it roll the soldier and guarden class's for the extra feets and jump moves makes the game to damn easy.
#4 neverwinter nights 2: this one is a combo of class and race go a pally as a teethling *think that was there name the devil race* and just stomp though everything. the pally is so freaking op in that game with the compaion you get that it makes you wonder why they gave you a choice really and going a teethling gives you nightvision makes navagating so easy that you will never spring traps if you take the thief with you.
those are just the games that i can rember off the top of my head but the point has been made BW can't balance a game to save there own lives.