Dual tanking is probably the most common sin of less than savvy Nullsec residents. It’s a common pitfall because the logic behind it is actually quiet sound.
“I don’t want to get killed out there, so I’m going to fit as much tank as I can. If shields use Mid-Slots and Armor Tanking uses Low Slots, nothing is stopping me from fitting both!”
It’s also supported by a lot of sci-fi background, in which most ships have powerful shields and thick armor plates. Unfortunately the logic and the corroborating literature do not equal a sound decision in EvE. The chances are, if you have (or do) make this mistake, it will be while your fresh and new to the game, when you have little to no experience of the mechanics.
So why is this a sin? First and foremost we have to consider the tanking penalties. We must understand the three key underlining principles of tanking; Buffer (how big your health bar is), Resistances (the % of damage you can ignore) and Repair Rate (how fast the bar will return to full). With both Shield and armor buffer has a disadvantage*. With Armour, your ships mass (and thus is velocity & agility) are penalised. With shield your signature radius is penalised (making you quicker to lock & easier to hit). This means that by dual tanking, you are going to be slower to get away and faster to lock. You are also going to be twice as easy to hit (Signature radius and speed twice the chance to hit mechanics). The net result of this is that your tank may have increased, but your survivability and your ability to avoid damage has dramatically decreased.
But it doesn’t end here. If you fit a dual rep ship, you are also removing your utility. Part of the balance of the shield types has always been “Shield tankers get to do more damage (low slots free for damage mods), armor tankers get utility (mid slots fit ewar, tackle, etc)”. By fitting a dual rep, your tank now takes up all your utility meaning that you will hit with the force of an intercontinental ballistic marshmallow, and have no ability to range control or perform ewar. A far better idea would be to fit the utility slots left by your tank with things which will help you avoid/remove/control the incoming damage while you tank. Shield tankers can kill the enemy faster with damage mods, and armour tankers slow the enemy down, speed themselves up or stop them from locking.
So is it ever excusable to dual tank? The short answer is No, but in honesty it’s more complex than that. Firstly this doesn’t include other less solid tank types (ewar, speed & stealth) which can sometimes be mixed to great effect (see assault frigates). Secondly, some will argue the dual tanking a bait ship is a good idea. This is because you no longer care about your survivability (your bait, you don’t have any), your only concern is to survive long enough for the cavalry to arrive. However the counter argument is that bait only works if they can point the enemy to prevent escape when the cavalry do arrive. This means they do need mid slots. My final advice is; when in doubt, never dual tank. You will be laughed at when you lose it (and you will).
This is a sin you tend to see later in the life of new Null sec players. It also generally also has two flavours; small weapons & big weapons, close range weapons and long range weapons. The former is generally because the player wants to be able to hit tackle and other frigates, the second is because they feel the need to hit an enemy at every range in-between here and Jove.
So why does it make kittens cry? Well this one’s pretty simple in actual fact; it’s a simple case of “jack of all trades master of none”. If your guns can hit all ranges and/or all classes of ships, you will not excel at killing any of them. In EvE ships are designed to force you to make choices (this applies well to dual tanks as well). If you think you have found a way to cover every option, the chances are you have missed something out somewhere. The tank and damage of ships are balanced assuming that the full DPS of a ship is going to be applied to the full tank of the enemy. If your only applying half (or goodness help us a quarter) of your DPS to a target, they are going to laugh at you and hit you back with a full rack of weapons.
Mixed weapons are occasionally excusable. For instance you won’t get laughed out of Null if you fit two Heavy Assault Missile launchers to a Auto cannon hurricane, nor will you for Using a Torpedo & Auto cannon Typhoon. But these situations are easy to spot; when you fit a ship look at its primary weapon type (hint: Ship bonuses, racial weapons & how many turret or launcher slots does it have most of). Fill your ship with this weapon type and if you have slots left over, you can use the secondary weapon system. If you find yourself using two types of turret or two types of missiles you will fall foul of this. In the case given above you can even justify sizing down the secondary weapon system (in the Hurricane example, using light missiles instead of heavys); but you may have to explain your reasoning (killing drones & tackle might fly). But in all honesty, you’re better off fitting a utility High, like a neutraliser.
Thanks for reading
*this applies to the rigs as well