You're right about the LucasArts stuff, a Standard ISD carries 60 turbolasers, 60 ion cannons and 10 tractor beam projectors. THe shipw as intended for siege to appear above a planet and bombard, as well as for taking on other starships, never for starfighters. The 60 turbolasers as distrubuted all over the ship but an Impstar has several external critical spots, shield generators, bridge, engines, hangar and the Ionization reactor. The targeting systems of the Impstar are also exposed. Impstars rely on the superiority of their starfighter to counter starfigther threat, because the turbolasers weren't designed to counter starfighter, they take to long to recharge, in comparison to anti-starfighter cannons. A single shot could most likely kill one starfighter, but an X-Wing flies at 90 MGLTs and a B-Wing at 85 MGLT, they are still to fast for the manhandled batteries. The same goes for the tractor beams.