Well this is going to be long but here go anyways.
Lucifer mostly suffers from being a mediocre middle child between Desolator and Cerberus.
Desolator is a good defense upgrade from all the previous available options at 1600 metal price, just slightly under 4 times the price of Stinger or Gauss.
[Spoiler]
It hits decently strong with 400 DPS and with good enough aim-speed that it can reliably hit air units in range.
It's main cannon has AoE letting it do Riot role against light unit swarms.
It has 10 000 HP as the heaviest porc tower HP wise.
It has 650 range that makes only heavier units and more expensive porc towers a threat.
It's heatray guns are neat I guess but you rarely get into situations where they help save the day because the cannon wasn't good enough.
It's only real weakness is that it's a medium-range static defense and can't move. An expensive golden baby of Stinger and Stardust that does what they do in 1 pricey package.
Skipping over Lucifer into Cerberus we get the first 'artillery' tower, at just 2500 metal cost, just 300 more than Lucifer.
Bread of butter of "I want to hold this ground" and rules over every previous defense tower you got as a great upgrade to get as any in your little porcupine den.
[Spoiler]It's got whooping 1850 range, nearly 3 times the Desolator range that lets it bully every other mobile artillery.
It's got same AoE per shot as Desolator at half the damage but it has 3 barrels to fire at once letting it oppress big clumps of units.
It can fire directly or in an over-head mode letting it fire if it's dug down into the terrain to protect it vs direct fire or to fire over terrain enemy might be hiding behind.
It's only got 3750 HP
It's main weakness is only 180 DPS, which requires just 4 shields to 'tank' that cost basically the same amount as Cerberus itself.
Now we come to the middle child Lucifer and comparison to it's predecessor and successor.
Precision anti-heavy turret from what it's description says with a heavy price tag for what it does.
[Spoiler]
It's got metal cost of 2200, 600 more than Desolator and 300 less than Cerberus.
It's got 400 DPS, 4000 damage every 10 seconds - Same DPS as Desolator's main gun. Nice 220 DPS advantage over Cerberus. Instant-hit attack however no AoE - Not regarding odd scenarios where units run into it's beam while it's firing like Lance experiences.
It's got 1200 range, almost double the 650 of Desolator and 650 less range than Cerberus. Hitting the "Long range" tier but not long enough.
It's got 6000 HP, downgrade from Desolator's 10000 but higher than Cerberus's 3750 so it can take a hit or two.
It's got 50 energy grid requirement, same across the board for Desolator and Cerberus as well. No energy drain, just minimum requirement of 50E/s which should be available in 10x the amount by the time you're throwing down Lucifers.
It can bunker down for damage reduction same as Desolator while Cerberus can not. An option rarely ever used and only really functional against nukes but it does require the 50E/s connection to do so and isn't the fastest at it.
It main weakness is that it's not excellent at anything really, whatever Lucifer can do you can get it done better by either Desolator, Cerberus if you want porc or Lance as a superior mobile version.
If you want more direct comparisons via metal efficency then:
[Spoiler]
Health per metal:
Desolator - 6.25
Lucifer - 2.72
Cerberus - 1.5
Damage(DPS) per metal:
Desolator - 0.25(cannon only)
Lucifer - 0.18
Cerberus - 0.07
Range per metal:
Desolator - 0.40
Lucifer - 0.54
Cerberus - 0.74
Alternative
Metal per Damage(DPS)
Desolator - 4(cannon only)
Lucifer - 5.5
Cerberus - 13.88
Metal per Range:
Desolator - 2.46
Lucifer - 1.83
Cerberus - 1.35
AoE per Attack
Desolator - 96
Lucifer - 0 - Technically some due to beam width+burst but practically too inconsistent to matter.
Cerberus - 96x3
Overall Lucifer just doesn't do anything particularly good that justifies building it instead of Desolator or Cerberus.
If you need frontline porc to hold the line then you get Desolator, cheaper so it comes up faster, more HP to tank the hits and same DPS.
If you need your porc to have more range than Desolator's 650 then instead of just 1200 range for 2200 metal Lucifer you get 1850 range for 2500 metal Cerberus, 650 range extra range over Lucifer for just 300 extra metal!
Sure you lose 220 DPS but at 50% more range than Lucifer you can just bully it from safety.
You might as well make 2x Lance for the price of 1 Lucifer, you get slightly worse stat performance but gain the priceless ability to move your anti-heavy weapon around.
Hell if there's an Impaler around with it's 1500 range the 1200 range Lucifer is at it's mercy, even the 1180 range Tremor can reliably damage Lucifer while outside it's range. For the 2200 metal price Lucifer is short ranged for the role it's supposed to do that Cerberus ends up being a straight upgrade.
There is also the issue of the counter porc sniping and how Missle Silo fits in that role with EOS missiles.
Desolator is the easiest to kill by sieging it, it has 10k HP but only has 650 range which lets a lot of things bully it cost effectively. But not EOS, it's 10k HP requires 3 EOS missiles which cost 1800 metal vs 1600 metal cost to build it.
Lucifer on the other hand has 6000 HP, which means it dies from just 2 EOS missiles that cost 1200 metal vs the 2200 metal cost to build a Lucifer.
Cerberus is similar with HP at 3750 which means it still dies in 2 EOS missiles that cost 1200 metal vs 2500 to build a Cerberus.
[b]- BUT -[/b]
Missile silo is the only "safe" way to kill a Cerberus due to it's 1850 range that outranges EVERYTHING that's not even heavier artillery or superweapon.
You can kill infinite amount of Lucifers with just 1 Impaler safely sitting outside it's range plucking away at 6k HP with it's 80 DPS. For Cerberus you either need shields covering you or cloak if you aren't going to use Silo or Super weapons.
Many ways to buff Lucifer to be better without it being too good:
Cut price to 2000
Buff range to 1500.
Make close down/open up work without energy grid.
Remove need for energy grid.
Buff damage - Either DPS or Burst.
Give it same sight range as it's weapon range.
[Spoiler]- The most expensive scout
Increase HP.
HP regen while closed down.
Pick your poison, mix and match if it still under performs ect.
TLDR: SKIP LUCIFER - MAKE LANCE OR CERBERUS