Just got round to trying out a squad of nothing but Ywings, and it proved very effective! The squad was Horton with an R2 and 3 Gold Squadron Pilots, all four with Ion Cannon Turrets, of course. I was up against Vader, Soonter and Turr, Vader with Engine Upgrade and the Interceptors with Stealth. I lost one of the Gold Squadron Pilots, other than that it was pretty one sided, not a lot they could do when they were ioned most turns, and the Ywings don't need to worry about getting them in their firing arcs.
Hortons ability didn't come into play very much, so I might drop him and see what else I can get for the points, maybe more astromechs, or torpedoes to cover range 3.
It's possible that this this worked in large part because I had the numbers; against a tie swarm it might not go se well, although it might still work - making them collide, plus the single wound will be pretty significant to them. I think it would work best against Firesprays and Shuttles, one straight forward could be disastrous for them, so long as you keep out of the Firesprays arcs.
So there you go, Ywings certainly aren't useless! Was a fun game to play, too.