Why does it seem that the Rebel ships that can take the most upgrades also have the least agility?

A while back I made a squad that was designed to shut down my opponent's actions. Two Y Wings with Ion cannon turrets and two B Wings with Tacticians and Flechette cannons. I initially did well with a few games, but the obvious weakness soon shown through: there is almost no agility. I could be taken out very quickly while my opponent flew circles around my ships.

Then later on I heard about another list that was doing very well: four B Wings each with Accuracy Corrector. So I tried that one. Again, initially did rather well, but again, the lack of agility killed the squad, especially against Phantoms.

(Side note: I do believe that Phantoms are overpowered, not because of the cloaking ability, but because of their attack dice. Four attack dice? Really? No other ship in the game has more than three.)

So now I'm trying to figure out another list that can shut down my opponent, but also has some agility in it. I'm not opposed to using Y's or B's, but I'm not sure if that should be the entire list.

Right now I'm thinking of using two Golds with Auto Blaster turrets (especially useful against Phantoms) and proximity mines. But what else should go in it? Hobbie Klivian with the stress bot could work, but I can't seem to think of a fourth ship to use that would deal some kind of stress or ion effect against my opponent that would fit into a standard 100 point list.

Any suggestions would be greatly appreciated. Thanks.