Oh my. Well I suppose I can't blame you for not searching the forums and reading the eighty+ posts I've made about not mixing guns.
And I suppose I can't blame you because I have been too busy to get dontmixguns.com back on-line after a recent server move.
So I'll repeat my rationale here because hey, that's the nice guy that I am.
Don't mix gun types.
Put as much firepower on a target as fast as you can.
Keep the target in your optimals.
Do the damage that the enemy is most vunerable to.
Keep transversal velocity of your target low for damage, high for defense.
And finally, be ready to switch ammo to compensate for targets that you can't catch, or get in too close.
Most people mix guns for the purpose of staggering ranges, which means at any given time, several of your guns aren't firing. Wrong. You neep ALL guns putting damage out ALL the time so that you maximize the damage you do with EVERY shot against a SINGLE target.
You want to get as many hits on a target as quickly as possible for the most damage you can. By mixing gun types, you're adding time it takes to kill the target--which is more time for your enemy to try and kill you.
Pick the best set of one gun type you can mount and put that on your ship. Maneuver your ship to keep yourself in those gun's optimal range. If the enemy gets too close or too far and you can't catch them, switch your crystals/ammo to compensate. Same goes when you're heading into a fight--if you've got 40 clicks between you and enemy, load up radios, fire your weapons, and then switch to gammas or multifreqs when you're within 10. Put as much firepower on your target in the shortest time you can.
Ship-to-ship combat encounters in EVE are measured in seconds or minutes. And the differences between a ship's damage output or it's armor or shields resistances is measured in single percents. People pay millions for modules and implants that do 2% better.
So if you're flying around with 6 turrets, and you've got two turrets firing at frigates, two turrets firing at cruisers, and two turrets firing at the battleship, you'll do absolutely nothing against any reasonable enemy pilot. Rats of course are a different story, but we're talking about PVP here.
Other games are programmed to allow the player to mix guns effectively. SFC3 was such a game--you were limited by the slot type to the size of the gun; on one ship, you could have 6 turrets but only 4 could fit large guns; the other two could only fit small "point defense" type guns. One strategy, called the Alpha Strike, called for the player to close on the enemy and fire all guns. But SFC didn't model optimal and fall-off ranges effectively, and it insisted on much longer recharge times for its weapons. Battles could go on for hours.
Not EVE. With one of the main measurements of a successful generic combat ship being DPS, you simply cannot afford to do anything but focus your fire effectively against your enemy.