For Small scale RVR/SC, I think 2h with mixing sets for extra stats is better, you take lot of strength for decent damage and still very tanky, but Glass cannon Black Orc can pump some big numbers, sometimes is funny to do it

Conqueror is an amazing set, but basically, make just YOU hard as hell, don't give anything to your group, while Vanquisher give a 3% reduce damage taken to all group (but as someone already said, proc on attack so is not up all time).
I prefer use Vanquisher as MT in dungeon and Sentinel as 2h OT, Invader for large scale RVR, Bloodlord for solo PvP or farm, and mixed sets for SC/6man rvr (depends on composition I can go more offensive or more defensive so isn't always the same, but still is based on mixing more sets)
So, in my opinion, Conq is not better than Invader, just they have a different role, still, I think that 7set bonus for Blorc is way weaker than BG/Chosen.