They are bad for one main reason, lack of thruster.
While you might think its no big deal, let me make a list of the problems it causes.
-Probably the easiest cap to kill in the whole game because it has battleship mobility and cruiser shield with a slightly better than cruiser armor.
-Totally useless vs BS since it has difficulty staying far enough due to lack of thruster
-Easiest cap to kill with a single GB because its a sitting duck. Yes you have lots of firepower, but if the GB pilot know what he is doing and thrust around you at about less than 100M from you, he is kinda hard to hit.