You are not the only one to notice that 6 tie fighters led by a force-sensitive should make short work of them and didn't. Especially since Ahsoka and Sabine practically treated that fight as a "warm up" and training! I mean, COME ON. If you notice,
Morgan also seems suspicious that Shin's forces didn't do much better. And while most of the pilots with her seem crap shooters, they were able to very deftly fly around the space-whales.
That ship has some impressive shields, obviously, but
of course they can't hold against a turbolaser hit and as you said, if Ahsoka was not on the wheel, they would not have to worry about the Turbolasers. They are not point-blank weapons, they are meant to target ships an order of magnitude bigger than this one.
Now, if Hera, Anakin or Solo was on the wheel, they could have slept right through the entire thing. Sabine makes some impressive maneuvers but she's simply an academy-trained pilot with some experience, nothing close to Solo, Hera or Anakin.
As for 6 tie fights being an issue... when the Rebellion attacked the first deathstar in episode 4, Vader got out alone, in his modified Tie-fighter and took down squadron after squadron of X-wings without breaking a sweat. 20+ veteran pilots were simply throwing their lives away to buy time for Luke to bomb the Deathstar and it still came down to Solo hitting Vader with another tie-fighter.
That is not to say that force sensitives are awesome - force sensitives that know how to use the force while piloting are awesome. Neither Sabine nor Ahsoka fit that bill and Ahsoka never had reason to be awesome or even good pilot.
When I see her taking command and sending Sabine back to use the guns as if she was Zeb I was
? And then we learn that Ahsoka "trusts in the force" so she deleted the guidance and presets for Sabine and I go
At first, I thought it was a mistake to be honest, but then I see Sabine fixing staff (She's a mechanic / explosion specialist that is very good but still not awesome with pistols - I expect Rex to be better than Sabine with pistols) and Ahsoka being a jedi. Till Ashoka had Sabine turn the wing for Ahsoka's magnetic boots to attach as if Ahsoka the jump-and-move specialist could not use the force to draw the ship to her or her to the ship... that was plain weird.
To surmise: No, I don't think an ex-jedi should be able to fly better. She never had reason to become an awesome pilot when she was surrounded by much better pilots. Every clone was a better pilot. Why would she train or practice? In the Episodes she has to chase people, she either hitches a ride or takes a train or something.