I did indeed expect that artillery would be in support or rear echelon formations, and spoke about support formations specifically. Remember that support formations get 25% the chance per unit size to be targeted by an enemy front-line formation as do front line formations (ignoring exploitations). This means that, although most of the time your bombardment formations avoid getting attacked, when they are attacked they get hit at full strength. The whole of an enemy front-line formation targets the whole of your bombardment formation in such cases, and surviveability suddenly become critical.
I've put armored and unarmored infantry-type bombardment in expeditionary forces several times ... and seen them take quite a lot of casualties. Put the light and medium bombardment in light vehicles, and losses are a LOT lower. Remember that light vehicles have 3x the HPs of regular infantry, which means that at even tech crew-served AP weapons only get a kill one time every nine penetrations.
Consider an enemy armored element, of tech equal to your own, with a gun capable of killing a light vehicle in every hit and also with an AP weapon. Now compare your armored infantry (2x armour) to your light vehicles. The gun takes out one armoured infantry per hit, and the AP weapon takes out one armoured infantry per 4 hits (2x armour versus 1x pen, 1x HPs versus 1x damage). Multiply this by the 0.6 base hit chance against attacking infantry, and you get a expected kill rate of 0.6 * (1 + 6/4 effective) = 1.5. Perform the same analysis for light vehicles, and you get 0.4 hit chance * (1 + 6/(4*9)) = 0.467 expected kills. The light vehicles are, in this case, more than 3x as survivable. Against typical enemy infantry formations, they perform even better. However, against enemy medium and heavy artillery light vehicle artillery would fare less well. If you expected a lot of hostile artillery compared to your own attacking forces (a situation I've never be in yet) then I would not use light vehicles.
For support-echelon bombardment units, my point is that light vehicles are sub-optimal not because they compare poorly against infantry but because a heavier vehicle type is better. Medium and heavy vehicles have more armor, more HP, and more weapon hardpoints (e.g. VEH+MB/MB brings more firepower per ton than LVH+MB). Since evasion is useless in support and rear echelons the armor and HP is much better to have.
As a side note, if you're deploying armored infantry as an attacking formation you really want to give them the HP mod as well as the armor, the highest level of which gives 2x HP for infantry. This bumps up the infantry survivability which is critical for an offensive formation that needs to maximize combat power per ton, rather than per BP as a defensive formation would. Of course that's a later-game research but it does eventually change the balance. Considering the case of equal tech enemy armor, say VEH+MAV/CAP. The MAV will always overmatch both INF and LVH at equal techs, thus dealing 0.12 kills per round to INF and 0.08 kills per round to the LVH (factoring evasion and 0.2 base hit chance) while the CAP will deal damage as:
- INF with 2 armor, 1 HP: 1.5 kill rate * 0.6 evasion * 0.2 base hit chance = 0.18 kills per round
- INF with 2 armor, 2 HP: 0.375 kill rate * 0.6 evasion * 0.2 base hit chance = 0.045 kills per round
[li]LVH with 2 armor, 3 HP: 0.166... kill rate * 0.4 evasion * 0.2 base hit chance = 0.0133... kills per round
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Total kills per round:
- INF with 2 armor, 1 HP: 0.12 + 0.18 = 0.3 kills per round
- INF with 2 armor, 2 HP: 0.12 + 0.045 = 0.165 kills per round
- LVH with 2 armor, 3 HP: 0.08 + 0.0133... = 0.0933... kills per round
In this case, the INF with 2 armor and 2 HP takes about 75% more casualties (in terms of individual elements), but due to tonnage efficiency you can deploy twice as many INF+CAP and come out ahead anyways. for LAV the infantry and vehicle are
close to breaking even, for LB or HCAP the vehicle is more tonnage-efficient. Based on this, it makes sense early on to deploy INF+PW (or PWL, PWI) and use LVH for any heavier weapons in an offensive formation, which is a pretty standard kind of Mech Inf formation, but infantry can close the gap once you get sufficient armor and HP mods (even the 1.6x HP mod should make INF+CAP competitive).
Of course, the classic use of infantry remains Zerging a bunch of space marines with some kind of PW to soak up all the AV fire while your tanks kill things. LVH will never be able to replace infantry in this role.
As for the Inf vs Light veh:
The meat shield effect is only worth while if your trying to buy time. If your trying to win the battle then the inf don't seem like an effective choice. This could simply be from my lack of experience but it seems like the ai goes inf heavy armies. If true the survivability of light veh and static should be more cost effective as a front line. If the enemies do have a more heavy weapon focused armies, then i could see a inf heavy front line being useful.
Mechanically, the main way the meatshield effect works is by absorbing AV fire that would otherwise OHKO an armored element. A standard MBT design might be VEH+MAV/CAP and weighs 62 tons. An enemy MAV can knock this out in one shot at equal tech. However, if you deploy half as many MBTs and escort them with an equal tonnage of INF+PW (5 tons), then about half of MAV shots in each round will be wasted on a cheap infantry unit and the overall rate at which you lose tonnage is reduced, keeping your MBTs in the fight and wasting enemy ammo.
Obviously CAP is the counter to this and enemy infantry are pretty efficient in this role as well, however both of these will waste shots against the duranium wall of your tank force which would otherwise kill off an infantry.
Essentially the net effect is that combined arms forces reduce the efficiency of enemy firepower while preserving your own. You lose
some raw firepower in the initial stages of battle but your force overall has a lot more stamina to win a large battle.
Inf are a bit less tonage but i couldn't really find a down size to being a large tonnage unit in combat. Sure they are targeted easier, but that doesn't matter for your main front line unit which goal is to kinda pull fire from your more expansive units. So its just a matter of needing a bit more transports.
On the offensive you always want to maximize combat power per ton. It's not a matter of "needing more transports" - if you have more transports, you
still want to fill those transports with the best optimized force that you can, per ton.
One thing i didn't see mentioned yet is inf have a 50% nerf in their ability to cause breakthroughs compared to vehicles.
This is a good point.