Before you start reading the following wall of text below, I apologize in advance for any misinformation and information that I may have missed.
With that said, stealth in Warframe has undergone several changes, for both good and bad. This however, will mostly point out my problems with the current mechanics of sneaking around the solar system. Here are those problems:
- Freshly Spawned Stealth Penalty; Back when the AI was still quite oblivious to corpses and enemies dying right next to them and Focus was still new, there exists an alternative method to farm a large amount of affinity with little time spent other than Draco's Interception. That method was to run Exterminate missions with Invis-Frames (Ash, Ivara, Loki) and a killing weapon of choice (preferably the one that kills most of the enemies in one go). Simply run past the enemies towards the extraction point, and all of the enemies left behind will be teleported to the next room / tile, allowing quick and easy kills. A few month later down the line, a fix was made to hinder that method. That fix, is the penalty timer that applies to a freshly spawned unit, preventing them from giving the stealth bonus, as well as breaking any stealth chain that's active. The method and fix is shown by these videos below, courtesy of AGGP and Darthmuffin respectively. With the recent upgrade to the AI awareness however, this fix should have been removed already. As it stands now, it's only becoming a hindrance to me, since I now have to both make sure the corpses stays out of sight, as well as waiting for a few seconds before deciding to kill that Scorch that I just saw at a distance, just to make sure the penalty timer wears off or risk having that 5x stealth multiplier reset to zero...
- Not-so-subtle Silenced Shotgun Kills; Back then, with either Banshee's passive or Silence, Loki's Hushed Invisibility, and the Silent battery mod, shotguns became viable for farming stealth kill bonuses, mainly because they're able to one-shot enemies with a well modded setup and/or a clean shot to the face. They also have the fun factor of flinging corpses around and can either fall down a pit for easy cleanup, or into an enemy's line of sight. Right now however, it's completely broken, unless you've manage to score a kill with just ONE PELLET. This applies to multishots as well IIRC. I'm not sure if this was intended or not, but it sure made leveling shotguns slower through stealth runs.
- Oversensitive Sleeping Sheeps; So I've found something odd related to sleep debuffs, not sure if it applies to blind as well. Whenever I use Ivara for stealth runs, there are two odd things that could happen whenever I pull off a Noise & Sleep Arrow combo to two or more enemies. The first is that whenever they are put to sleep (and remember that they will end up sleeping within arms reach of each other due them converging to the Noise Arrow's location), every time I killed one of them, the rest within the 5 meter radius WILL be alerted. And for the second one, is whenever I walk up to them from the front uncloaked. For some reason, they will also be alerted as if they weren't sleeping in the first place. Now I may just be nitpicking these particular details, but if you were to be put in a deep sleep yourself, and someone was killed right beside you, will you be able to notice it?
- No, You Can't Share These Stealth Affinities Anymore; For those that have witness a friend / teammate doing a stealth kill back then, the affinity gained from that kill is the same as the one who did the killing, meaning that stealth killing was also an alternative to helping friends rank up their equipments, getting large amounts of affinity for not just the one doing the killing, but for the rest of the team as well. With my recent runs with my brother however, the affinity gained from me stealth killing an enemy won't be applied for my brother, as he only gained the affinity that enemy would give when killed normally (I gained around 4k-ish while he gained the usual 800-ish for stealth finishing a Bombard). Because of it, it ends up being faster to just go guns blazing through endless missions together while the stealth kill bonus is better off used for solo runs.
Edit 1: I understand that all of the problems I've stated above are related to grinding. And as it stands for me, stealth right now still has some challenging aspects (maybe it's not challenging because I'm mostly using either Loki & Ivara for that, but it's mainly for speed-grinding daily syndicate rep), but downright impossible to experience it unless you're running solo most of the time. If there was another small problem I had with stealth, is that stealth killing with most damage-oriented warframe powers doesn't count, even if it manages to oneshot enemies (melee channelling skills such as Excal's EB, Wukong's staff, and Valkyr's Hysteria still counts IIRC)
The other thing about stealth is that as of right now, there isn't much use of stealth to its fullest for the rest of the mission types other than Exterminate, Rescue and Spy...
Wanna do a Relic run stealthily on non-endless missions? Void Fissures says Heck no, we'll be spawning in full on alert mode, so good luck sneaking through this one.
What about Capture? Sure, you can sneak past the guards till you spot the target. But as soon as Space Mom announces that the capture target's in sight, the whole tileset will be set on full alert mode immediately, and that target will quickly rush to the nearest excape pod. Oddly enough the earlier versions of Capture missions doesn't alert the entire map. Heck you could actually do a stealth takedown on the target if done properly.
Mobile Defense? Like Capture, you can sneak around till you reach the console. But everytime you insert the payload to hack it, all bets are off, and enemies will rush in guns blazing. Why can't we just quietly hack the damn things if we could get from console to console undetected?
Sabotage? Depends on the tileset. If it's to destroy the old reactors aka. the 1.0 versions or to deliver a data box to a console (Old Deception), then it's doable. Ship Sabotage 2.0 however, will have you battle it out in the open regardless of you choosing to set it on fire or freezing it. Hive & Orokin Sabotages are both highly impossible to do a stealth run, where the former involves the Infested, and the latter involves a fully alerted map right from the start.
Hijack? Well, you're literally stealing large and precious cargos out in the open, so enemies will notice that regardless.
Assassination? Sneaking until you've reached and left the boss room is fine, but it'll be very hard to avoid direct combat during the actual boss fight.
Endless Missions? Well, the point is to either guard something out in the open (Defense), playing king of the hills (Interception), or creating distractions long enough for the infiltrator to collect your reward every five minutes (Survival), so stealth is not an option there.
Archwing? Yeah, good luck with that side of the game...
All in all, stealth runs in general is still viable, but with the problems I wrote above, it doesn't give me any further incentives to do stealth runs other than preventing the alarms from being triggered, and sometimes getting the daily syndicates rep cap & ranking up some equipments. Challenging, it is at times, but rewarding, it is not.
What do you guys think? Should the stealth get reworked again in any form? Or would a simple removal of that spawn penalty timer be enough?