Lets look at the one Scourge unit all of us are using. The Desolator is your command unit, and is required in clash or battles (games above 1000pts). Its a beautiful model in your Scourge force, but its often hard to quantify if she is worth her points, as she can be difficult at best to use in games.
So lets take a look at the Desolator first in more detail. (the above model was painted by Blue Table Painting, I only wish I was able to paint this well, and this year at Valhalla I plan on spending some sit down time with BTP painters there. Shawn is a good friend of mine, so I suggest taking a look at what they can do)
Desolator
The Desolator is your Command unit. Its expensive for what it is, coming at 140pts. When a new Scourge player is buying new units, past the starter set, the Desolator is one that definitely adds the points quickly to your totals.
With that, we do get some decent mobility out of it, as it comes with 6 damage points and an armor of 6. This helps it, as it moves forward, but will need some air cover as it can be vulnerable to enemy fast moving flyers, or other units trying to pick it off.
I have been frustrated with the Desolator more than I have liked it. Its problems start with not being able to keep up with the movement of your primary Scourge forces, so if you plan on using this models in the fight, you must keep the battle somewhere mid field.
In games where you start in the corners, you will have a hard time getting this unit into the fight if you push the battle towards the enemies back lines (this has happened to me several times). Because of this, and of course the fact that she needs to be up front and personal with her attacks, it makes the desolator a harder unit to use.
The Desolator's attacks are a ton of fun if you are able to use them. (using them only in the last round of the game does not count, but this can happen if the battle moves too much or is too far away).
The gun is an Ion Storm Generator which comes in two modes of fire.
Focused
In its focused mode, its incredibly strong E13 and comes with demolisher d6+1 (which means it just wrecks buildings hardcore). Like always though the gun is short ranged in this mode, 6" with a move and fire of 9". In this mode, the gun is great for finishing off any buildings in forward positions that still hold enemy infantry.
Wide
The wide version is of course the most fun, as it blasts downwards to the ground, and out in all directions up to 12" away. Models caught in short range are in trouble, and hit on a 3+, while those outside of 6" are hit on a 6+. Its a strong hit, and likely to do some damage, and if your opponent lets you get off more than one blast with the this, the desolator can really start to clear a heavily populated area quickly.
One important thought with the desolator. It is your command unit for Scourge, but do not put your highest level commander in a single Desolator. This is a front line unit, that will not last the entire game if she is being used aggressively. If you have more than one on the field, then its OK, but this is a high priority target for your opponent, and not one you want to cripple your command with if you lose her.
In large games, I have put a level 3 command in her, but most games, the cheapest command you can get; level 2. I tend to put my higher level command in my Annihilator artillery to insure a strong command during the game. (another option is putting them in your heavy tank squads if they are large)
Command for Scourge is important. It gives you the initiative you need in winning the round choosing to first or second. It gives you the ability to get the cards you may need. Get your Scourge a high level commander, but do not automatically put them in the Desolator.
One last thing, there a cards that let you re-roll to hit with a single weapon. Save these for the Desolator's Ion Storm Generator. Its devastating when firing it in wide mode. Also consider using more than one of these command units. While I have not tried it, its on my list of things to do if I pick up another one of these days.