Canonic Perfection
vs.
Gameplay.
Canonic Perfection is a target goal, but...
Gameplay takes complete priority in a dead heat. Even so, there are canonic justifications for the implementations of the Star Destroyer here.
The Star Destroyer is well suited for long range assault due to the advanced nature and sheer quantity of its weapons. It can move quickly enough to keep fast Rebel and Pirate craft in range, then pummel them senseless with their guns. However, things get a lot dicier when a brawler-type capital ship, such as the highly durable Mon Cal cruiser.
Note the ISD getting fragged by a Mon Cal in Ep. 6. Presumably, it had help in the form of B-wings; but the ISD probably had its own bombers imperiling the Mon Cal. Note that the Mon Cal was in point blank range.
The ISD makes a great carrier, though. Hence why its a standoff vessel in these maps, suited for launching fighters. You'd have to be a stupid Rebel cap ship driver to close with the ISD, given the power disparity and proximity to exiting TIE Bombers. And even when Gallofree transports have to get close to the ISD, the ion cannon on Hoth prevents it from using its most powerful systems.
Patience, people. No doubt you'll get a rough n' tumbling full fledged Star Destroyer soon enough.
GC Veteran (0.14-R6) "General Jafar"

