I love "The Survivors". The mystery was strong. I had no idea what was going up until Picard spelled it out. The actors portraying the Uxbridges brought themm so vividly to life which was essential in pulling off the tragic ending. TNG used battlescenes sparingly but the engagements between the Enterprise and the marauder were exciting.
It was also one in a line of many TNG Twilight Zone-inspired episodes with the bizarre and cool image of the lone tract of green land with a house in the middle of a barren wasteland or the maddening music that tormented Troi to keep her from seeing who Kevin really was.
It is an A episode and one of my favorites.