“We had almost reach the objective, the Dark Reapers were giving us excellent cover fire, all we had to do now was plant the charges and run. Suddenly a loud sound of rockets launching could be heard all over the battlefield. As I turned around, to my horror, The Dark Reapers had being blown away. Immediately I knew it was a whirlwind, but before I could order the vipers to handle it we had already being ambushed by a group of Space Marines who fell from the sky wearing jump packs. I was the only one to escape that horrible day, we were so close to victory…how could I have not foreseen the whirlwinds attack?”

Deployment
One of the beautiful things about the Whirlwind, is it doesn’t need line of sight.
You can deploy it wherever you want and it will still be able to fire at full effect.
Having said that, the best place to deploy the whirlwind is at the very back of you deployment behind some terrain, depending on the size of the board your using you may want to deploy it a bit closer to the middle of your deployment. From here your whirlwind will be able to steadily pummel away at your opponents armies without too much fear of retribution.

It’s often a good idea to deploy a small 5-man tactical squad with a heavy weapon in line of sight to the whirlwind, as a “just in case” way to make your opponent think twice before he tries deep striking a unit to get rid of the whirlwind and to stop any land speeders or the like heading straight for the whirlwind.
And hey!  The more thinking your opponent has to think the more likely he’ll make a mistake.

Battlefield Role
The Whirlwinds role on the battlefield is fire support, usually against mass numbers.
If there’s a massive squad of grotz, which you cant/don’t want to get messed in with, that’s when the whirlwind steps in.

Targets
Always make sure your shooting at the right unit, firing at a unit of space marines wont achieve too much. Always try to target a unit with an armour save that the whirlwinds missiles will ignore. This way, all you have to do is wound the enemy, which usually shouldn’t take too much with the missiles strength 5. With a range of 48” (on a standard 4’x4’ board) you’ll be able to reach what ever you want, and as long as your good at guessing ranges the scatter hopefully wont move out of place too much. So you’re bound to get a couple of hits with that nice 5” blast template.

Notes
Armies which Whirlwinds do well against: Imperial Guard, Tau, Eldar, Dark Eldar, Orks, Tyranids and Kroot Mercenary Armies are all very vulnerable to Whirlwinds due to their poor armour saves or toughness.

Armies that Whirlwinds aren’t to good against: Space Marines, Chaos and Necrons.

Upgrades: Don’t bother giving the whirlwind any extra upgrades such as extra armour and such. Usually an opponent won’t bother sending anything after a tank worth only 75 points.