I don't know how to solve PvE & T4 + implants. We have now special encounters wich are exploitable and players which have them as main target in the game farm them easy enough.
But let's return to main topic. I don't see a reason why more PvP dungeons should be added. You can take formula
[online_players] / random(4,6)
and you will get the real number of the players here. All the rest it's only crafters in own tents, botters, se farmers, Hubbers, etc.
New PvP area needs new PvP activity.