The Fire Warrior squad lies at the heart of every Tau army. Not because they are an amazing unit however - its just that you are forced to take at least one squad in every force! There are only a few units in 40K that are completely compulsory for an army - Tau Commanders, The Emperor's Champion and Necron Warriors is all else that springs to mind. This compulsory choice means that no Tau general can become competent without mastering the way of Fire.
A squad of Fire Warriors consists of 6 to 12 Shas'la - the ubiquitous troops of the Tau Empire. If you ante up the points you can upgrade one Fire Warrior to a Shas'ui, and he gets a bonus +1 Leadership... oh yeah and an extra Attack (at Initiative and Weapon Skill 2!). The additional Leadership of the 'el is most valuable in a larger unit.
Let's compare the stats of the Tau with the humble imperial guardsman. Firstly the Tau have a measly Weapon Skill 2, and Initiative 2, which leads to them getting consistently slaughtered in close combat, even by a humble guard squad. Their only defence is their 4+ armor save. In contrast to a troops like the veteran guardsman in carapace armour, who has a better Ballistic Skill, the Fire Warrior has among the weakest stats of any basic troop in the game.
Thats it. Fire Warriors don't get any special abilities or fluffy rules. Presumably because they don't need them?
So what do Fire Warriors have that guardsmen don't? A very nasty Rapid Fire gun called a Plasma Rifle. This weapon is Strength and AP 5, and has an amazing 30" range. Make sure you understand how the Rapid Fire rules work - the distance to the target required to activate the move and shoot twice ability is always 12", even when the weapons total range is more. Pulse rifles can cause a lot of casualties with a bit of luck; but they are hampered in effectiveness by the squads low Ballistic Skill, and the preponderance of cover in 5th edition.
A couple of markerlight hits utilised to cause 24 S5 shots to hit on 2s can be a devastating combo - but never forget that those same 'lights could also be used to drop your opponents cover save or Leadership. With 2 markerlight hits against an enemy in cover, you are statistically better off to use one 'light to get +1 BS and the other for -1 cover save.
Sometimes it might be easy for you to do enough wounds to force a Leadership test on an enemy unit that you urgently need to remove from the battle (and is not Fearless). In thise case, it could possibly be a better use of those markerlight hits to modify the ensuing Leadership test.
The Pulse Carbine is the humble cousin of the Pule Rifle. It shares the same Strength 5 but trades in 30" Rapid Fire for 18" Assault 1 Pinning. Once less shot when within 12" of the target, but you can still assault - like that matters!
Pinning has so much promise - the chance of basically stunning an infantry unit for a round, like it was a vehicle. This could easily cause a failed charge, or leave any unit that dared stray out of cover as a sitting duck to any counterattack. Unfortunately pinning in my experience is one of those abilities that you can take or leave. First you have to find a unit that is not Fearless - and Leadership tests are rarely failed anyway. It does combine extremely well with Marklight hits used to reduce Leadership.
The true strength of the Pulse Carbine is that it allows the Fire Warrior to move out of assault range of its target unit and still shoot effectively. The ability to pin the assaulting unit synergises brilliantly with the overwhelming fire power of the rest of the Tau army. Any unit pinned in the Tau firing lanes is in big trouble.
Tragically Fire Warriors are given no options for heavy or special weapons - it appears that they are forced to shoot down approaching Rhinos with their pulse rifles - they do glance on 6s after all! This is a big issue as it makes the unit ineffective against a large chunk of some armies.
Being a pushover in close combat is not necessarily a bad thing in 40k. If they are attacked by a close combat unit, their big fear will be wiping the Fire Warriors out in one round of combat, leaving them stranded in the open ready to get blasted off the table by the Tau players firebase. This is why you should never take photon grenades, they help your opponent by minimizing their attacks, giving them a better chance of staying in combat that extra turn. Any points spent improving the Fire Warrior's melée ability are points wasted.
EMP grenades however are a more interesting option. They are actually not a bad weapon, glancing on a 4 or 5 and pinning on a 6 - once they hit of course. Awesome against Land Raiders that haven't moved - but how are you going to get close enough to a Land Raider to use them? So they are situational only and don't synergise well with the unit's other activities.
The Shas'ui is the only squad member to access to the following upgrades. The bonding knife lets you rally when under half strength. useful when a fleeing unit rallies to return to an objective or not give away a kill point - but only with larger squads. The Shas'ui can take a markerlight for a good price - and then the hard-wired target lock becomes an option, allowing the valuable markerlight to be fired at the optimal target. Don't forget though that the markerlight is a heavy weapon - so you cant move the unit and fire effectively. At least he still has his pulse weapon for these situations.
Finally you have the option to buy drones, but I do not think they are worth it in a cheap unit like Fire Warriors. Drones are fragile because they are killed instantly if their controller dies. I'll go into more detail about drone options when I post my review of the Crisis Suits.
Fire Warriors on the table seem to have a target painted on their armour. Against shooting they have Toughness 3 and a 4+ save that everyone gets from cover anyway, and a low Leadership of 7 or 8. In CC they just die. Putting them in a Devilfish is the answer. It immediately provides them the protection of armour 12, and 11 on the side. Cough up for the 5 point disruption pod upgrade and suddenly you have a troop carrier that takes its cover save where ever it goes - at least until the opponent gets in to melta range. This is awesome, and makes the price of the Devilfish actually worthwhile.
There are two levels of upgrade for the basic Devilfish descriped above. The first is to buy a multi-tracker, so that you can shoot one weapon when moving at cruising speed. As the gun drones can fire if any of your weapons can, this means you can fire 5 S5 shots (with 2 pinning) whilst moving 12" - actually quite good! The second level of upgrade is, in addition to the multi-tracker, trade the gun drones in for a smart missile system and targetting array. The main advantage of this configuration is that you no longer give up an additional point for the gun drones - but at a considerable points cost. I am not convinced I must admit. With 7 S5 shots the targetting array definately becomes worth the points, but now you are paying alot
Score from Reserve (145)
6 Fire Warriors with pulse carbines
Devilfish with disruption pod
A cheap unit in a Devilfish, this is the most efficient way to run a Fire Warrior squad. Avoiding upgrades keeps the unit cheap. The purpose of this squad varies depending on the mission type. In objective missions, they start in reserve and come on from your table edge, then move forward to hold objectives as required. In Annihilation, they start in reserve, then come on the board as far away as possible from anything dangerous - and stay there! Six plasma rifles won't do much, but the the slight chance to pin from the carbine could be enough to save the game. I have avoided the multi-tracker because they should be in reserves or away from the action most of the time.
Rapid Response (240)
12 Fire Warriors
Devilfish with disruption pod, multi-tracker
The idea is to take a bunch of rapid firing S5 and drop them off where ever there are infantry models. Combines with a couple of marker light hits, they can cripple a unit of light infantry and even kill a few Space Marines. The Devilfish can add noticeably to to this weight of fire, even after moving 12" to drop them off.
Solid Gunline (150)
12 Fire Warriors with Shas'ui with bonding knife, markerlight, target lock
This is what you get when you invest some points into a Fire Warrior unit. This unit is designed to sit in the safety of your back field and lob pulse rifle shots at enemy foot troops or low armour vehicles. The Shas'ui is a good purchase here as his Leadership 8 makes a big difference to the squad's morale. The bonding knife might stop this expensive unit from running off the board late game, allowing them to attempt to hold an objective or save a kill point. Now that we have spent so much, adding another 15 points to give the Shas'ui a markerlight that he can shoot at whichever unit needs it most is not a bad deal - its just a pity that markerlights are heavy weapons.
Kroot Alternative (100)
10 Fire Warriors
A bit more pricey than Kroot, but perfect for a Fire Warrior themed army. At least they have little chance of surviving their opponents charge, leaving the victorious unit desperately consolidating towards the nearest cover. The purpose of this unit is to provide a screen in front of the firebase of your army - and shoot at anything that makes itself a target. I have gone for 10 models so they can form a considerable road block to any advance, and its a good number for moral checks (need 3 casualties to force a check, need 6 dead to flee off the board).