The Whirlwind tank is one of the weaker armoured tanks, comparing on the level with your basic Rhino rather then that of the predator. But that is not to say it's weak.
The Whirlwind houses an ordnance missile launcher, which happens to be the space marines only guess weapon. And second ordnance weapon. It's got a nice guess range doubling that of the vindicators ordnance range, combined with medium hitting power. However it's largest advantage is that it doesn't need line of sight when firing. It doesn't even need to see the enemy.
So even though it has weaker armour then the average tank, it's weapon system more then makes up for it, and in a way makes its armour a non-issue. Since there is no need for you to see you enemy, there is no need for you to let the enemy see you, hence denying them the chance to blow it up.
Deployment is everything for this tank. Place it not only in cover if possible, but also preferably behind something. Be it hills, template of fores,t rocks piles, or anything that will deny your enemy line of sight. Due to it's range it also advisable that you place it as far back as possible, its range should still leave most targets within range and no need to move.
Because your whirlwind launcher is an ordnance weapon, you can't fire if you move, even if you move 1". You should not move, nor have a need to with this tank. If you have to move, then move 12" because even if you move less you still can't fire. So there is no loss.
The Whirlwind is best-employed verse swarm or horde like armies. Due to it's medium strength but large template it's an ideal weapons verse these types of foes. This is not to say it doesn't work well verse others such as chaos or necrons but it's not as effective due to their higher toughness and better saves. It is also good verse light armoured foes, such as transports and the like. Though it doesn't have a high strength it does still roll on the ordnance table and gets 2D6 penetration, making it a good chance to do a good deal of damage.
Actual tactics are rather simple and straightforward; most have been covered already in fact. You want to deploy behind a piece of terrain to deny you opponent sight of the tank, and preferable towards the far end of the table. You shouldn't need to move, and you don't want to, as this will stop the rain of death, as I like to call it. After position, the only other thing is to practice on guessing distance (something that takes some time to master) and just keep on firing. Keeping in mind what the tank works best on, and aim for the great threats there on out.
You should be able to keep the cost of the tank relatively low. You have no need for extra armour, and I'd even go so far as to say there is no need for smoke. If you keep it in cover or behind it and out of sight, you can't get shot at. Hence there is no need for it. As far as other upgrades go, these are also wasted and not needed. This leaves you with its base cost, which is the same as the cost for a Typhoon. This also makes it the cheapest tank in a space marine army, and in my opinion one of the best tanks there is. Its largest flaw besides it's low armour (almost a non-issue) is that it's armed with a guess weapon. For the untrained they can be a little unreliable at first. But as you get used to using it more and more, this also becomes a non-issue, to the point where it's not even guessing. Not much else can be said about this tank. It's cheap, hard-hitting, straight forward, and easy to use tank. It's easily capable of dealing with hordes of troops. What else could one ask for?
Hope you enjoyed the MT.
Inkaras
[Note: since this tactica was written, the rules governing firing have changes- eliminating the tiresome "guesstimate".]
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The Whirlwind is my favourite SM unit, I take 2 whenever I can. My whirlwinds are by far my army's MVP. They always pay for themselves in battle, always pin at least 1 key unit during a battle, and I'd say are only destroyed in 1 out of 10 battles (unless I'm playing against SW scouts, they ALWAYS kill my whirlwinds).
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The whirlwind is one of my favourite pieces of kit, I've never (that's right, NEVER) played a game in which I didn't take one... and it has very very seldomely let me down.
Aim for the backsides of tanks, with a little practice and 'range-testing' (firing once just to get a general idea of the distance, firing twice for effect) you should be able to do some pretty nasty things, like covering 2 tanks' backsides in one go... or covering some 8 marines under the template.
Never forget about the pinning tests the enemy incurs for every time blast that hits in which they suffer any casualties... it also has a -1 modifier from 'barrage'... meaning the Whirlwind uses this as yet another way of paying for itself, since it can temporarily disable important enemy formations.
