Could you post your favourite loadout, in terms of the frame you use, the weapons you use, and their mod configs? I can give more tailored advice with that information.
sandriver
Give her augment a try, since it turns her into a nuke frame. I wasn't a fan before the augment either.
Voruna is an outstanding frame, being an agile, highly mobile, invisible nuker with super easy energy economy, at least if you run Ulfrun's Endurance. She's able to project extremely spicy slashes over a wide range through the combined action of her 2 and 4. The mobility afforded by using Dynar's passive is both fun and effective for what she wants to do, and she has gap closers in the form of Raksh and Ulfrun.
Lycath's Hunt is self-sustaining if you keep priming enemies with Raksh, and kills from Ulfrun will count as melee kills to spawn health orbs, meaning Voruna should essentially never run out of energy.
The conditions for the +dmg/-acc corrupted mods are basically "high accuracy, low crit, low status". I use Magnum Force on Hildryn's Balefire.
Stacking base damage always grows linearly, which can beat crit on weapons with bad crit stats, and can beat status on weapons with low status chance, but will very rarely beat both, and usually on very old weapons.
I think the shield gating changes and Secondary Fortifier have done wonders for his survivability and chill factor.
More broadly it sounds like I should cover his survivability techniques and tools?
I think the Limbomb build is essentially dead on SP. I couldn't get it scaling properly even with Panzer viral and fullstrip. For all I know it's bugged and doesn't properly account for the SP health multiplier, like how Oberon's Reckoning didn't used to account for the SP armour multiplier.
Limbo has been through a few iterations, how about his current state and how the game has changed to give him tools to mitigate his pain points? For example, Zariman was kind of the Limbocalypse due to Overguard, but he has Fortifier and Magnetic to deal with that mechanic now. I also didn't join until 2015/didn't get seriously into Warframe until 2021, so I personally just can't speak for launch Limbo.
Styanax is a beast in Circuit since his Final Stand spears scale off the amount of decrees you have. He's easily one of the best Circuit frames, standing alongside Nova, Vauban, Gyre and Protea for hard-scaling Circuit nukers.
To be fair, Styanax is a beast everywhere due to the raw power of Final Stand (especially augmented with Overguard) and Tharros Strike. If you're not in Duviri, the projectile ability scaling can be tapped with Arcane Arachne.
I was on Switch at the time, and even with the godawful load times it was my favourite content. Whenever I had relics to crack I'd drag the clan with me into Void Storms, or even just solo Corpus Void Storms. The thing that killed Railjack for me was the introduction of SP fissures, since the value proposition of doing a soft-endurance endless fissure is way ahead of anything else in the game.
I'd still recommend Void Storms in a heartbeat to new players though. They're hugely valuable everything farms with credits, endo, and preradded relics.
As for Railjack itself, I really like the quality of life of universal affinity and shared loot, as well as the collaborative nature of the objectives. It's cool playing with my friends and operating as a team, which is basically unique in Warframe in its current state.
I like your idea. Instead of Overguard I think your idea of exceptional DR plus party-wide status immunity would put her on par with Dante's utility.
I misremembered, Steve read out someone who commented that during the preview devstream: https://www.youtube.com/watch?v=T6Vy7OkcXc8
There are at least three Dystopias in the game, lol. CN Dystopia, Professor Dystopia, and you.