What rebel build would be the most damaging against 4 blue squadron novices each with R2 astromech and Integrated astromech?

Super dash would give them a hard time for sure. You could add Miranda with TLT. They would be hard pressed to deal.

The best squad to run is something that is versatile. Something that can deal damage as well as take it. The T-70 is a broke ship, but it does have weaknesses. Just be sure to avoid jousting as you could have one ship receiving 4 3 dice attacks. My buddy likes to run squads similar to this and I usually run turrets to avoid having to stress and turn around after the first pass. Since there is no room for autothrusters, they get whipped by TLT;s or ions.

Ion Torps and Assault Missiles encourage your opponent to keep space in his Squadron. One on one, these pilots aren't as tough. Remember the Tallon Rolls, and try to avoid getting caught in too many arcs once they are broken up. Warden Squadron Pilots and playing for the init bid may be a good place to start as well. TLTs and pick your ordinance. I like one with Advanced Slam plus Proximity Mines; one with Ion Torps, Extra Muns, and Guidance Chips, last one plain TLT. Gives some variety, but as long as you avoid concentrated fire, they should do some work. It would at least be fun, whether it wins or not.