Turrets aren't dead but rebel turrets are pretty much dead at this point. I saw the final match at a store championship yesterday between a friend of mine running a great dash corran list, not the 58 dash but dash with lone wolf and recon against 2 aggressors with auto thrusters.
Right now the decimator with vader is the only consistent turret that can punch through auto thrusters but you're killing yourself in the process.
Frankly, the reason your friend lost was because he wasn't using the 'standard' 58 Dash. Lone wolf + recon won't cut it because you need both actions for BR + boost. Whereas PtL + kyle + HLC allows Dash to eat aggressors for breakfast with (ideally) minimal return fire since he's @ PS7 (vs PS6) and as long as he's around the asteroids, he has a huge advantage.
4 dice attacks turrets 'should' still trump autothrusters, although I'm not super math savvy, so I can't prove it. So HLC dash is still a strong choice I think.
As for the decimator, Chiraneau w/ Expose + EI + ysannne Isard should still be very strong against anything with autothrusters (maybe throw in merc co-pilot so range3 is not 'weak').
Even a gunner build should be able to work, since your opponent will get bad rolls eventually.....right? Like Chiraneau w/ predator or PtL, gunner + engine upgrade. I haven't played with any of this, admittedly, but I'm not sure 'the sky is falling' on decimators just yet...