Darn it, every one beat me to the punch. Okay, since the new BSG is set up on a basis of naval combat (Oh, by the way Ron Moore use to play the online version of Harpoon back when it first came out on the net).
A modern naval carrier group travels with four to six escorts (which is why Ron Moore has said 'of course there are other ships besides Battlestars, but most if not all of them have been destroyed and weren't shown'). The primary threat to a carrier during the cold war was land-based aircraft and enemy surface ships/submarines. Soviet doctrine called for massive waves of bomber-launched anti-ship missiles attacking from 2-3 axis and more sub or surface-launched missiles to form a 3rd or 4th axis of attack.
American doctrine called for waves of fighter patrols assisted by radar and jamming aircraft (Hawkeye and Queers in the Navy, Raptors in BSG). The F-14 was designed so that it could launch six Phoenix Missiles at six targets at a range of over 100 miles. They would launch at bombers if the bombers had not launched missiles already, or at incoming missiles. Medium range fighters (F-4 or F-14) would take out incoming missiles with Sparrow/Sidewinder shots. Remaining missiles would be engaged by surface vessels firing Surface to Air missiles, and point defenses (Basic Missile Defense, Five Inch Guns, and Phalanx Cannons) would then fire at surviving missiles. As a final measure, chaff and flares would be launched by all ships, and a cruiser or destroyer always sailed close to the carrier so they could 'jump in front of the bullet' to save the carrier - yes, naval doctrine calls for a smaller ship to sacrifice itself to protect the carrier. They even carry decoys to make smaller ships LOOK like the carrier on radar so they will attract the missile instead of the carrier.
BSG combat works on very similar principles. The Vipers are to take out incoming bombers and missiles farther out from the ship, while the ship itself has weapons as a last-ditch point defense effort. They also are set up to provide a 'zone of fire' so intense that they can destroy entire waves of incoming fighters. Lasers don't work well unless it's at close range, and projectiles can travel forever until some gravity source slows them down and eventually pulls them in. That's why projectiles are far more deadly in space than some laser beam (which should be traveling so fast that it wouldn't be visible to the naked eye anyway...I mean look at real life lasers, do you see them passing through air or just reflecting off their target?)