As a Assassin Darkness/Madness hybrid i want to cut in and explain why Guard isnt gamebreaking.
Tanks in PVP have the same damage mitigation as most classes and most damage ignore our shields, defense and theres a ******** of armor penetration aswell.
I have a easier time killing a Jugg or Assassin and their mirrors then a Sorc or Commando forexample as defensive stats dont mean squat.
Tanks role in this game is to be supportive in PVP not tanky. If Guard would be nerfed/removed we would loose our role in PVP and just end up being useless.
As long as we cannot be true tanks in PVP we remain supports!