Both Bastion-turret and Torb-turret have the same core strategy, that is, you land behind a corner, sneak out, pop off a rocket, then get back into cover before they can acquire you as a target. You can rapidly change direction much faster on the ground and if you get in trouble get out.
Splash the ground/wall behind them if you are in close proximity or can't get out without exposing yourself to more direct fire.
Point is not necessarily to kill them, but force them to reposition/move/do something that isn't just spam damage at your team.
Bastion-recon is probably the most dangerous hit-scan-hard-counter to you and as posted above, it's all about who see's who first, with the following caveat: You have about three seconds to land two direct hit rockets INCLUDING TRAVEL TIME, so odds are if even if you get your second rocket off and kill him, by the time your rocket gets there you are already dead.
In other words if you engage a Bastion-recon you must be able to deliver two hits in the three seconds since it saw you.
If you can't do this, get out of there, the odds are against you and you're no good to the team dead.