It was the 3rd Nebula I encountered (After Epsilon Erdani and Mourners), so the only modules I had were Bomber (Just how strong are those, anyways?), Flak, and Translocator. I maxed out my missile module for it, but it's just not enough. I could probably do it in the hull one up from Destroyer, but not that early.
No Zenith hull is unfortunate, and the Neinzul hull is almost never useful in the Nebulas. So, Human hull Destroyer. That means 12 small and 3 large hardpoints.
Large hardpoints are the most important, so let's look at them first.
Against the RS, Missiles get the Ultra-Heavy multiplier, so they do 150,000 DPS per Mark = 450,000 DPS per module at Mk III.
The only other Heavy module with Ultra-Heavy multipliers is the Plasma Siege Cannon - you neither have the module, not the hull, so not useful.
Bomber Bays produce 3 drones every 5 seconds, with a 21 second lifespan. That's a steady state of about 12, and each drone will be able to fire 5 times during its lifespan. Each shot is 14,400 damage, but Bomber drones have the Ultra-Heavy multiplier (as well as Structural, Heavy, and the coveted Command-Grade), giving each drone a 52,000 DPS. With 12 drones, that's about 620,000 DPS.
In addition, Bomber Drones can mess up the targetting priorities of your enemies (same as the Neinzul Enclave drones) which is sometimes useful. Against the RS, you want the DPS instead, so you'll be using your Shadow Shield to protect yourself, your drones, and your allies (and the stations).
Small modules... well, Flak and Translocator are useless in nebulas, unfortunately, along with Acid Sprayer, Nanosubverter, Insanity Inducer, and (usually) Paralyzer. None of the small modules have Ultra-Heavy multipliers, so you're stuck with the base Damage for normal modules. Against the RS, the highest base damage normal module is the Paralyzer, at 17,000 DPS per mark. Unfortunately, you don't have it.
So, the special modules: Polarizer, Impulse Reaction Emitter, and Doom Accelerator.
Absolute best small module is Polarizer - RS has 1,000,000 armor, so the Polarizer gets the maximum 100x multiplier to base damage, 55,000 DPS per mark, for a whopping 165,000 DPS at Mk III, all Aromor Piercing.
The Doom Accelerator is as complicated as usual, doing between 5,200 and 46,800 DPS per mark. Best thing to do for planning is use the average estimated over the target's entire lifespan, 50%, as the multiplier. That gives the DA 26,000 DPS per mark, or 78,000 DPS at Mk III, again, Armor Piercing.
Last is IRE, where the huge Energy usage of the RS also gives max multiplier of x30, or 30,000 DPS per mark, for 90,000 DPS at Mk III,
but not Armor Piercing.
But since you don't have any of those modules, you're stuck with Needlers (7,200 DPS per mark, 21,600 DPS at Mk III) as your best small module.
Assuming 1 shield, 2 Missile IIIs, and 12 Needler IIIs (plus the Human Champion's main gun) you'll be getting:
300,000 (main gun) + 2 * 450,000 (missiles) + 12 * 21,600 (needlers) = 1,459,200 DPS. You can up this to 1.9 million DPS by sacrificing the Shield module for another Missile, but that's a little risky. Not a bad idea (Shield III is only 11 million HP - half of a Shadow Shield), though. Total is about 300,000 DPS after armor is applied.
With 3 Bomber Bays and 12 polarizers, you're looking at 300,000 + 3 * 620,000 + 12 * 165,000 = 300,000 + 1,240,000 + 1,980,000 = 4,140,000 DPS.
As you can see, the Polarizers alone out-damage your best possible DPS with normal small modules AND all the Polarizer damage is Armor Piercing. Total 2.3M after armor.
Photon Lances are actually not a very good choice here. First, the RS moves a LOT during the first half of the scenario, so you'll spend a lot of time missing. Second, they average about 75,000 DPS per mark - about half of an equal mark Missile module.
And as all the comparisons above show, this is a scenario where your equipment choices are paramount, and make all the difference between almost-easy and nearly-impossible.
As for the Malfunctioning Gatlings Nebula, I think it's in a good place. I had a game where it was my first nebula, and I beat it just fine.
Mass Photon Lance also works for the RS (then again, if you have enough of those they work for any nebula really), but the grey spire malfunctioning gatlings one? I've rarely had trouble with it, and a good amount of the time its my first nebula. All laser and shield modules, and placing shields over the allies does pretty well. Doesn't always keep the forward base intact, but I've never lost that one. Certainly have lost to the RS more than once however.
Before entering any nebula, I kill Guardposts to get to level 4, and unlock Shield II and Missile II. This is just about ideal against most Starbase-killing scenarios, but is terrible against the Gatlings (Heavy hulled). Only Laser and Plasma Siege modules get an anti-Heavy multiplier, and I don't unlock/upgrade them that early. Also, it requires some heavy micro to keep you and your allies alive - I usually have to retreat to get repaired at least one when this is the first scenario. When it's the second, and I haven't unlocked bomber bays (or some other drone bay), I rarely win it.
I find that the Bomber Bays are the best, because the combination of Bomber Drones getting anti-Heavy multipliers and the Gatlings getting confused with targetting allows you and your allies to take a lot less damage while dealing out a lot more. Other drone types work for the targetting confusion part, although the damage is much less. Slicers actually do OK here, since the Gatlings frequently stop moving, allowing the melee to actually execute the full 1 attack per second.
But I hate getting the Gatlings on Nebula #2 or #5, since the number of Gatlings keeps going up, but you aren't *quite* to your next major power-up yet.