An excellent Warhammer Fantasy Battle tactics article from darthweasel, one of the Battle Reporter forum's most respected members.
The Warriors of Chaos are an interesting army. They have quite limited range, with only the Hellcannon, Marauder Horsemen armed with throwing axes or javelins, or magic able to do damage outside of close combat. This makes it imperative for the Warriors of Chaos to quickly come to grips with the enemy.Unfortunately, they are also hampered by being among the slowest armies. Their cavalry is equal only to the slowest of enemies and some armies move 1-2” quicker in the Cavalry wing. Meanwhile, the infantry is slower than the various Elf armies, slower than the Ogres and Skaven, and faster only than the Dwarf army
This means the Warriors of Chaos, an army for whom speed is at a premium, are at best an average speed army. As a result, armies with excellent shooting capabilities can often pick apart the elite Chaos Knights and Chaos Warriors before they can come to grips with the enemy. How to deal with this problem?
How about a unit with M7, T4, and W4? Enter the Dragon…Ogres.
At the same time, their 4 wounds apiece means they have to be shot a lot to keep them from reaching their goal which will generally be done in 2-3 turns at most.
With a base S5 and 3 attacks apiece, they will normally hit 50% of the time and wound at much higher rates. So they are a potent force the opponent must respect.
The downside is clear; their high cost of 65 points apiece means with no upgrades, 3 of them cost 195 points, just 5 points left than a unit of 5 Knights with no upgrades.
So lets compare the 2 units.
Their speed is even, their strength and toughness are even, the Ogres have the advantage in wounds and the Knights have the advantage in attacks (5 Knights with 2 attacks = 10, plus 5 Horse attacks at lower WS and S, 3 Dragon Ogres with 3 Attacks have 9 attacks). Both cause Fear, the Knights have a vastly superior Armor Save and the Ogres are immune to Lightning-based attacks.
Clearly, for similar points they have similar capabilities. The Knights have more possible upgrades, which can be a tremendous advantage as the addition of a War banner gives the +2 to the Combat Resolution, an option the Dragon Ogres do not have.
By contrast, the Dragon ogres have one giant advantage over the Knights. Whereas every wound done to a base 5 man unit of Knights reduces their effectiveness by slightly over 20% (Unit Strength), the Dragon Ogres do not begin losing effectiveness until they have taken 4 wounds.
Do not underestimate the importance of this. With LD8 and the Will of Chaos, the Dragon Ogres pretty much have to be killed to the last Ogre. With their re-rolls for failed panic tests, they will pass a whopping 89% of their tests.
This means they are highly effective in fulfilling dual roles.
First, their imposing presence and death-dealing capabilities will draw a tremendous amount of attention from your opponents. They will concentrate firepower and magic on them. Now, it might seem silly to use 195 points (or more if you upgrade them) as target presence. But they can withstand an awful lot of firepower and still be a threat when they get to their target.
Additionally, it will allow you to bring your game-winning units, say Chaos Knights, into the positions they need to be in to get off their lethal charges.
Second, the combination of 4 wounds apiece and M7 means you are likely to get at least a couple of them across the field. 3, 6, or even 9 S5 attacks can take out a lot of gun lines or, given Great Weapons, perhaps even a monster or two.
Sure, the cost is high, but as a Special choice, you can still fit in a unit of knights and a unit of Chosen if that is your chosen configuration…or even 2 units of Knights, and that is at less than 2000 points.
Consider this; you take 2 units of knights with full command and Mark of khorne and a unit of Dragon Ogres with Great Weapons you have spent 791 points. Throw in a Sorcerer with a couple Dispel Scrolls for your general and you are still under 1000 points which you can use for core units, Exalted heroes, and whatever your little heart desires.
That is a small, compact, hard-hitting force that can move quickly to deal with any threat the opponent can offer.
Additionally, who do they come after? If they divide their fire among your 3 Special unit choices, you already have achieved an advantage through the principle of divide and conquer. If they concentrate on one unit of Knights, they leave the other unit and the Dragon Ogres free to attack their chosen targets. If they choose to target the Dragon Ogres, they leave 2 units of Knights unmolested and 2 fresh units of Knights can do tremendous damage to any battle line.
By including Dragon ogres, you force your opponent to make a difficult decision, and any decision they make is only good for you.