I almost exclusively fly Dominators and Onslaughts, and I think you guys make good points. Lack of range is mostly the problem for these big slow ships, which is why ALL my low tech cap ships/cruisers have an integrated targeting unit, and Gauss Cannons in the large slot hard points. Almost all med points are used for flak/double flaks, while the small points are either rail guns, light assault guns, or vulcan cannons. Missile slots are pillums or reaper launchers if facing other caps. Other tech sometimes includes auxiliary thrusters, or extended mags/missile racks. With a setup like this they are tremendously effective. Gauss cannons/railguns lower shields almost instantly, even on the high tech ships, and will smash through armor too, albeit slower than high explosive weapons. The high explosive damage is covered by either reapers, pillums, or the light assault guns (or the 3 Hephaestus on the Onslaught). Light assault guns might not seem threatening to a larger ship, but when you have 4/6 of them firing they drop things very quickly.
The other benefit of this setup is that you are nearly immune to fighters, bombers, and missiles because of those extended range flak guns. Even frigates cannot kite around you because the combination of extended range railguns (with their fast projectiles) and flak demolish them if they dare to come close.
When setup like this, these ships are amazing, but I've found nearly any other setup to be lackluster. The problem comes from lack of range on non railgun/gauss ballistic guns (which is being addressed in the next release, but also the slow projectile speed of most ballistic guns. Frigates can dodge auto cannons easily, so if you want to hit smaller ships you need to use rail guns and flak. The second issue might not really be a problem, rather a weakness, but it does limit your options.
