Actually, Lancers and Destroyers are capital ideas...
And HC's take out large targets but get holes punched in them by smaller ones. That is where I came up with the idea of Defense Cruisers. It took about a month of going back and forth between Rezo, myself and a few others, but we eventually decided that a DC would be a wonderful compliment to the HC. Basically, its partner. HC takes out caps/cruisers, DC takes out frigates/SC.
Once again read my mod (it is after all devoted solely to adding new ships)... If not, I'll explain it here in a brief summary.
Lancers have very good linear acceleration and have the highest linear speed of any capital. They are giant tubes, so it makes sense. However, they also turn incredibly slowly. This makes them easy pickings for the fast and agile Destroyers. Lancers also have 80% of their firepower forward facing with much of it focusing fire, thus making them cap slayers once they get lined up. The level 6 ability is the activation of the axial cannon which is a death sentence as it either does insane damage, or in the case of the Vasari, bypasses shields/mitigation and heads straight for the hull, knocking out any hope an enemy would have of saving the ship.
Destroyers are faster and more nimble than lancers. Though they cannot outrun a lancer, they can out-maneuver one. By simply staying away from its bow, Destroyers can quickly take down lancers with their vast port and starboard weapon banks. Their damage is enough to take down lancers, but not enough for a battleship. Battleships will always win a 1-on-1 with a destroyer due to their abilities to counter and absorb vast amounts of damage. The Kol is a rock. The Radiance returns your damage by absorbing damage as AM, and the Kortul just counters everything you throw at it.
This creates a combat triangle out of the combat oriented caps. Sure, others like the Marza can do battle, but only the ones I just listed are truly meant for direct combat.
Also, it should be mentioned that the artillery frigate is a separate suggestion from the lancer idea...