Well let me first say, i understand that issues I gonna describe it are probably somewhere near the bottom of of dev team priority list currently while incoming Mainline with Grendel and Melee 3.0 are close and we still have Railjack and Duviri Paradox under development but on the other hand some of these fixes might be very easy and possible to sneak them into a hotfix or as a portion of Mainline update.
So with this out of the way, I'm writing this down mainly because I'm bit of codex completionist, but some of the recent additions to enemy list felt almost like attempt on punishing such attitude or forcing grind into another aspect of this game, or both at once, and this also hurt the role of codex as our in-game source of knowledge about enemies if getting this knowledge feels like as much of a grind as getting some rare drops, and this pushes more and more people into this mindset of "who cares" making codex become slowly more and more irrelevant what shouldn't really be the case for feature that can be very helpful.
#1: Inconsistent scanning standards
Well this is something that started way back with Alpha Ghouls needing 20 scans as "boss type" enemies during 1st appearance of this event, and even if this particular problem was solved then later we have way more of it
here is list of Eximuses that have number of scans above standard of 3, and as much as I could pass on 5 scans then 20 is way too much for something that is supposed to be "rare" version of enemy also this list don't cover another group of enemies that have the same problem which are recently added Demolishers with Devourer, Expired, Kuva Guardian, Anti-Moa and Charger, needing 20 scans while other types of Demolishers need just 5
Fix to this would be to simply change the current numbers and set a standard for future additions, just keep it consistent
#2: Ridiculously hard to get or obscure enemy variants
So this is frustrating when you don't know what to do to get one specific entry completed and it demands to do some ridiculous things to encounter this variant of an enemy like Manic Bombard Eximus demanding to get a lockdown in the manic holding tile before releasing them or even better example
And as much as the Manic one is something that has clear rules to how to cause it, the Jackal one having to perform something like this not even for a consistent spawn but for merely chance shouldn't be a thing, the chance of this Jackal variant should be higher and not demanding to cause basically double alert state, make the rules of how to cause this encounter clear and allow for something more than chance
Another thing from this category can be Vapos dropships which are hard to find and usually they fly out of the tile before a player has a chance to scan them
One more thing under this category might be Eximuses of Vapos Elite Rangers due to fact they are fairly scarce on the new Jupiter due to fact of them having a limited amount of tiles they can spawn on and also falling under the 1st problem
Next portion of this problem are areas with 2 tiers of enemies something that probably started with Orb Vallis and Elite Terra units but seriously became problem on new Jupiter with new Vapos units and fact that increasing levels of enemies don't increase chance of meeting some of the Eximuses, because they're getting rolled out of possible options in favor of higher-tier enemies and their Eximuses
Like situation when getting scans of Eximus of something that should be most baseline enemy is considered a rare find is simply not right, and my suggestion how to fix it is to allow regular and elite variants of these units to have wider range of levels when both can spawn, high enough that there is a decent chance for Eximuses of them during endless missions like Defense or Survival, before we reach levels of lower tier of enemies being rolled out of spawn table
#3 Conservation targets
So this is bit on the personal side of things but conservation targets scanning was quite annoying since this activity was added and so far there are still issues with it, addition of pheromones made for a weird situation that most common and rarest variants of species are easy to get to scan them but the middle rarity is still really hard to get it to spawn.
Fix for this would be the addition of specific pheromone for the middle rarity variant that would cost bit lest than pheromone for the rare variant, or make pheromone have 50/50 chance to spawn middle or rare variant
#4: Missing or confusing entries
This one has quite a bit to unpack, starting with Mite Raknoid still not being in Codex even if other Raknoids including event-exclusive Coolant ones are present there, other things are confusing entries like Demolisher Nox being listed as just Nox, or new variant of Hyekka that supposed to show up only on Kuva disruption but seems like so far no one encountered it to get even one scan and provide graphic to Wiki, these are oversights that should be taken care of but seems like these are case-specific fixes so might need more consideration
#5: Concerns about future
So with these problems in mind there is also matter of potential problems coming up in future, one of them is continuing to handwave current problems while they do hurt Codex as feature and it's usefulness, future additions to Codex should be held to a specific standard and not treated like something that will be fixed later while some of the problems I mentioned haven't received fix for quite a while (Mite Raknoid being best example)
Another Concern is Railjack and fact that many of the potential new entries gonna be spacecraft, what means that as long as we don't get some sort of ship scanning device, only option to scan these will be to fly out of ship on archwing and scan them with hand scanner, or by killing them with arch-melee equipped with astral autopsy mod what might be very problematic
#6 Not enemies entries but still related to scanning
Left as last because it goes slightly off topic but there but these are still related to scanning mechanics, so one thing is... Orb Vallis Somacord tones and the absolute ridiculousness of how they work, seriously if you want to encourage players to play Orb Vallis more then add more content, the scannable collectibles like that on open maps shouldn't be based on RNG, just put them around map in similar fashion like the Data Hashes or Mem Fragments and this will be much better way to deal with these because having to search around enormous open area including its cave system for randomly spawning item is just ridiculous
Another thing I've noticed is new single fragment in "Cephalon" tab right after the 3 entries from Mask of Revenant and not sure where to search for it or what it contains, especially that seems no one has found it as there is no info on wiki either, so if this information isn't some sort of spoiler I would like to know where I can search for it
I hope that this feedback will be helpful in both solving these problems and preventing similar issues form happening in future.