JohanJ wrote:
My main army is Biel-Tan Eldar and one of my two premium assault formations is eight Warp Spiders with two Exarchs in a Vampire. It is IMO an amazing attack formation.
Comparing that formation with 6 Wraithguards and a Spirit Seer in a Vampire for the same cost
Several very important points are missed off the earlier comparison:
(1) The Warp Spiders have jet packs which mean that they can deploy up to 15 cm from the Vampire.
(2) They have infiltrate so can ignore ZoCs in positioning.
(3) The Warp Spiders have First Strike so can effectively clip a formation (combined with (1) and (2) above).
(4) The Exarchs have inspiring putting the formation up +2 on resolution.
(5) The Warp Spiders are more numerous so will suffer less on outnumbering penalties.
AND in subsequent turns
(6) The Warp Spiders mobility means that they will have an assault threat range of 45 cm (cf to 30 cm)
(7) The Spirit Host drops its initiative if the unit with the Spirit Seer is lost (barrage or sniper or casualty).
(8) The Spirit Host is smaller so easier to break with BMs
(9) Spirit Host can shoot with the wraith cannon at 15 cm without engaging in an assault.
(10) Spirit Host has Farsight, provided the Spirit Seer is still around.
The slight correcting in numbers of attacks was noted by SpeakerToMachines, as was Inspiring.
I have struggled to put all these intangibles together into a simple simulation/post. Here was the simplest idea I could come up with. Lets see both attack, by Vampire Air Assault, a 13 strong, Arm 5+ (due to armour or cover), FF 5+ infantry formation, with no BMs. Like an Imperial Guard Infantry Company. Numbers assume average values for dice. This also means assume equal throws for resolution.
Vampire, 8 x Warp Spiders + 2 Exarchs: 2 x FF 4+, 10 x FS FF 4+,
positioned after counter-charges, so that only 9 of the target formation are within range.
Eldar cause 3.33 kills on FS and 0.67 after. Enemy cause, (9 - 3.33)x(2/6)x(3/6) = 0.95 kills.
Resolution:
Eldar (9 remaining, DC2 + 7 WS), inspiring +2, kills +4; Enemy (9 remaining), kills +1
Which kills another 5 enemy stands. Total of 4 remaining enemy units.
Vampire, 6 x Wraithguard + Spirit Seer: 2 x FF 4+, 7 FF 4+, 6 MW FF 4+
after counter-charges all are within range, with Wraithguard in front.
Eldar cause 6 kills (3 regular and 3 MW). Enemy cause 1.08 kills (on RA 4+).
Resolution:
Eldar (7 remaining DC2 + 5 WG), kills +6; Enemy (7 remaining), kills +1
Which kills another 5 enemy stands. Leaving the enemy with 2 units remaining.
These two assaults come out with essentially the same results. The Spirit Host looks more brutal on the first contact but actually the Warp Spiders do rather well on kills during resolution. The Spirit Host has 1 BM (4 away from breaking) compared with the Warp Spiders 1 BM (6 away from being broken).
If you move towards a larger target formation then the Warp Spider ability to clip is relatively more important.
Harder cover or stronger armour tends to help the Spirit Host.