OK so pvp balancing which was pretty damn good at launch isnt very good now, I can only assume that smash/sweep spec for example was underperforming in pve against vigilance/vengeance which is why they buffed it when it was already a top performer in pvp. Even the PT/VG "nerf" could be considered a buff as sticky grenade/dart is now off the shared cooldown allowing them to backload even more damage.
We have the expertise stat, personally I dont like it but we have it anyway so why not actually use it to balance out pvp instead of just being an arbitrary static number.
For example if an ability is under performing, say shock (I know shock isnt under performing but was first thing that came to me) then you could increase the modifier that particular ability gets from expertise from say 1.0 to 1.1, giving it a pure pvp buff and not touching the precious PvE "metrics"
Same goes for abilities that are horribly, mostrously overpowered, that attain damage numbers the likes we havent seen since stacking adrenals and relics, like say.... I dont know.... sweep and smash, then you could lower the bonus modifier from 1.0 to 0.7, again, not touching PvE at all and presto, nice and easy balancing of PvP.
That to me is the simplest way they could do it and wouldnt be much work.
What you and other people don't understand...
If you create a new damage table for PvP (or just shift it to another stat) then you just create additional testing and balancing issues. Now the developers have to check twice the results every time they make a change. Now its twice as long to roll anything out.
It also creates discrepancies with player expectations. "Hey! This ability usually hits for 2000 in PvE, why the heck does it only hit for 500 in PvP?"
There are many, many reasons to keep the game consistent. Not to mention that PvP gear is often mixed with some PvE gear based on how the player wants to build their stats. This solution, while neat on paper, would be a mess in real life.