As to your main point, yes, gunboats are powerful, they're also fairly easy to take down. If the gunboat is close enough to use his primary turrets on a cruiser, the cruiser should be ripping them apart. I've seen it, i've had it done to me, i've done it. If a GB gets close to a cruiser, the cruiser wins, hands down. It has many more guns, and as such, does much more damage/second then the gunboat can, couple that with its larger shields and most gunboats won't even get to the cruiser's hull.
