My idea for a *balanced* Star Destroyer was this.
Obviously, you can't put a ship that's as powerful as Star Destroyers are canonically, otherwise it would be able to burn right through Star Trek ships with ease, and Trekkies would run around complaining.
You can't give it craptastic specs either, or Warsies start complaining.
Since to the Empire the Star Destroyers were about the equivilant of CA's, I gave it CA-level specs.
A Star Destroyer has 60 turbolaser cannons...turbolaser cannons are relatively innaccurate and degrade rapidly with range...pulse phasers are the same, and fire 6 little blasts per shot.
So, you put 10 pulse phasers arrayed in front and side arcs, and you have 60 turbolasers, and the approximate firepower of a well-refitted CA (technically, probably more firepower, but no long range weapons and large and easy to hit, so anyone who's smart will snipe it with torpedoes from range 15 and beyond, taking out the weapons advantage).
And don't forget 2 360 mytronics for the 60 ion cannons the ship is supposed to have. Ion cannons disable ship systems temporarily- just like Mytronics.
The result is a well balanced ship, that with proper flying (get in close, tractor and slam them, hope they let you) can take on a Fed DN, and with bad flying will lose to a Fed CL (fire at long ranges, let it snipe you), and is overall a match for a well-refitted CA.