So I tried a "3 Cobra" army recently at the Winter Warmer, Westbury, preceded by an attempt against an Ork Mega-Gargant based army. Results were rather dismal, partly due to poor play on my part, and also poor dice - but you can't have everything
But it did get me thinking about things a bit.
Cobra MathsThe niche role for Cobras is against titans, where they can excel - but not always, which is the main point of the thread.
Given that each hit causes ~3 damage, and that you get 1/2DC dice to roll, the formula for effectiveness against titans is
where DC is rounded up to the nearest even number, and 'to hit' is dependant on whether the Cobra is 2BP or 3BP,
This gives the following formula for damage caused by a single Cobra depending on whether it is Sustaining, Advancing or Doubling
- 2BP - Sustaining: 1/2 DC, - Advancing: 1/4 DC, - Doubling: 1/8 DC
- 3BP - Sustaining: 3/4 DC, - Advancing: 1/2 DC, - Doubling: 1/4 DC
It is worth noting that adding a model to the '2BP' version turns it into the '3BP' version, but if the Cobra is already 3BP, using a pair does not improve the maths per se. But the 3BP version
does become much more effective against other targets, and a pair becomes realy lethal against all targets.
The other thing to note is that dice results are discrete - they do not follow smooth graphical results. This means, you are more likely to achieve the desired results with more dice (against larger titans) and less likely to do so with fewer dice (against smaller targets). Put another way, Cobras work better the larger the titan - DC6 and over, while they are both less reliable and less cost effective against WE that are DC4 or smaller. This is because you really need two and preferably three sustained shooting attacks to kill an unshielded enemy titan.
However, being aggressive against titans relies heavily on winning the strategy roll-off, as the Cobras will usually die if the enemy goes first. Unfortunately, the odds are not that good.
- Against Marines and BL, Eldar have a 42% chance of winning the SR (assuming the opponent wins the 1st turn - otherwise it is a paltry 27%)
- Against Eldar, the loser of a previous SR has a 58% chance of winning the next round, otherwise its 42%.
- Against Orcs the odds are reversed, giving the Eldar a 58% chance of success.
Equally the Eldar need to pass the initiative roll, which is at best a 5/6 chance (2+), but can easily be reduced to 2/3 or even 1/2 with a BP and / or retaining. This further reduces the odds of several Cobras carrying out a successfull attack to ~33%, although the presence of the Autarch does raise the odds to ~50% at best.
IMHO it is these odds that are the real reason why Cobras tend not to do well against titans.
Play StyleCobras can be used in three broad ways; defensively, aggressively and as opportunists. However, correct placement of objective is paramount and the initial locations of the Cobras will significantly impact their effectiveness, and the Eldar player needs to keep the Autarch on the table during critical periods to have the re-roll available.
- Defensively, Cobras can be very effective Blitz guards. One or preferably two in a corner on OW make a very tough target to crack by ordinary troops. They get AA against air assaults as well as OW shooting with TK weaponry, and potentially need several attempts to dislodge them - especially if guarded by Rangers or another formation.
- If you are going to use Cobras aggressively, they need to be able to move after opponents that can hurt them - so generally you need a high activation army (~12+ activations). This is especially true for killing titans as previously described. (but see the maths above)
- Opportunist use of Cobras sees them located in terrain (to reduce the potential for enemy fire), in places where they can pounce on smaller enemy formations and defend against enemy incursions.
The problem is that aggressive and opportunist strategies are difficult to play, and can often be easily thwarted by the opponent - eg by having a screen positioned around the titan target, or by having several medium or small titans.
Development optionsThe following extends options considered before which could also be combined, but not all will appeal to eveyone.
- Increase the range to 45 cm
Would give them greater reach which would make them more forgiving of poor initial placements and better able to shoot past screens. - Remove the Forward Fire arc restriction
This would make them more lethal as a static guard and more forgiving of poor positioning during the game. However it does not reflect the apparent design of the Cobra which has not turret. - Make them initiative 1+
This would significantly improve their chance of activating, but still leaves the strategy roll-off as the single most important factor in their success against titans. However it is contrary to the generic Eldar list design, and would make the Cobra better in other situations. - Make them DC4 or improve the armour to RA 4+
Either would make them more able to survive losing the strategy role, which in turn gives them a better chance of sustaining at a critical point. Neither are unreasonable given the way the Cobra has to be put into a 'suicidal' position to achieve the goal of destroying an enemy titan. However both options are contrary to the generic list design, and may make Cobras too good in other roles. - Reduce their cost
Mentioned for completeness, but not desirable for many reasons. - Increase the firepower to 3BP
This does not really assist killing titans, while it does make the Cobras better all-round killers. Not my preference, but should be considered. IMO the issue is whether it makes them too good as a singlton and especially as a pair. - Revert to Ignore Cover against all targets
Reverting to IC against infantry and vehicles obviously makes them better against these targets, which may be desirable if they cannot be improved against titans. However this does remove an annoying anomaly in the stats. - Ignore Shields
Boosts the attack against WE targets while not against other targets. However, as Cobras need not rely on other formations to strip the shields, this potentially boosts the rest of the army. It is also another 'special rule' - Increase the TK damage value
Boosts the damage to WE targets while not affecting other targets. Could be a single number (TK5) or used with a variable (TKD3+2) etc. This would also boost the ability to kill smaller titans with a single Cobra. Few if any downsides other than a possibility of distorting the balance against titans (taken to the extreme a 250 point Cobra might kill a 1050 point Mega-Gargant in a single attack which could be seen as a little excessive)
(Edited to include other options mentioned earlier)