It is pretty obvious why they won't see a ton of play, compare the following:
Delta Squadron Pilot (38)
TIE Defender (30), Heavy Laser Cannon (7), Twin Ion Engine Mk. II (1)
vs
Patrol Leader (40)
Or even:
Delta Squadron Pilot (30)
vs
Bounty Hunter (33)
For only two points you can upgrade a fat defender to a turret that spits out nearly the same attack and has a whopping 16hp! For three points you can upgrade a generic defender to a generic bounty hunter which has an aux arc and more health. The defender depends way too much on its dice and not maneuvering, which I don't find as satisfying compared to interceptors, where my input matters a great deal in how the game turns out. When the dice are good a defender can outlast these but I've had defenders die after only receiving two attacks. Poof! There goes 1/3 of your list, try to recover from that...
The Defender relies very much on maneuvering, it just relies on planning ahead and working your way into situations where you have an advantage. It is proactive, not reactive. The payoff for an Interceptor's maneuver is that turn, where you arc dodge or pull into range one. They payoff for the Defender's maneuver is one or two turns later, where you've set up a couple turns of HLC fire on a ship spending actions to dodge asteroids.
