People overstate the power of Star destroyers all the time. The Falcon outruns 3 of them in the break from tatooine, and evades more in Empire. They are not great at hitting small fast ships. This is best done by having lots of restricted firing arcs that still let them pump damage into big ships, but create holes fighters can hide in. The whole reason the Interdictor was made was because Star Destroyers sucked against fighters. Hell, I believe there's a scene in empire where one of them loses their command center to an asteroid. I just read about it the other day.
Exactly. And yet, a single Star Destroyer engaging a squadron of small, fast fighters, in the middle of an asteroid field, with few or none of its 72 TIE fighters for support - that feels authentic to you? Star Destroyers were designed for ship-to-ship combat and orbital bombardments. Wouldn't it have a better "feel" to field a picket ship that was actually designed to be an imposing monster to any fighters it came across? Why try to shoehorn a familiar ship into a role it never actually filled?