I completely agree with Ion Cannons on the TIE defender. You are going to use a cannon with every shot, since it can attack with both, so you need a cannon that is useful every turn.
Tractor beams are not useful every turn, and they don't do damage on their own. They are worth it for a 1 point option on a ship that has an open slot, but they are not worth filling a slot that you intend to use every turn.
When they work right, they are the only thing that will work that way, but you aren't even going to get that situation once in every game. Throw them on a shuttle which isn't filling the cannon slot anyway, or the second aggressor slot, or a G-1A to give it barrel roll and it is the best 1 point you can spend. Put it on anything where you are planning to use the cannon and the opportunity cost of filling that slot is way too much.