Concealed Fatigue is an upgrade tree based all about losing one's sight. Top branch of the tree is all about sacrificing one's sight for increased damage and exp magnet range. Bottom branch is all about rewarding players for eliminating enemies in the darkness. Concealed fatigue is a very cost effective way to get the benefits of multiple different trees at once, all at the sacrifice of your vision circle/cone being nuked into blindness. It is a high risk, high reward upgrade tree, but isn't very rewarding anymore for the risks it asks for.

Well, when alone it is a powerful tree, but unfortunately it will always be alone because it has no synergy. The main sacrifice, vision, is a cost too steep for the buffs you get if you remove it completely.

Colossus Part 2 didn't add anything else for concealed fatigue, in fact it is even stronger than it was before!

Vision is a main component of the game, and many are reluctant to give it up. Vision allows players to spot enemies before they land a hit on that enemy. Basic advice to new players is to pick one of two upgrade trees that increase one's vision size, because the enemies get faster over time, and the reaction speeds needed to counter them can be mitigated by simply seeing further. This sight alone makes vision strong, and can be seen as a crutch easily relied on by many.

Vision is great on its own, but the reason why concealed fatigue isn't worth it anymore is because of synergy. As the game development progresses and new upgrades and perks come out, vision continues to get more synergy while concealed fatigue continues to be pushed further and further behind. For instance, let me list some of the upgrade trees that synergise with vision and some of the trees that directly nerf or have no effect on concealed fatigue.

• Light Target
  
• Light Meteor
  
• Radiation
  
• Plasma Charge
  
• Shield Barrier (Bottom Branch middle upgrade buffs vision by 50%)
  
• Gleam
  
• Spotlight
  
• Proximity Marker
  
• Windup Strikes (Bottom Branch marked targets only appear when in vision)
  
• Swiftness (Bottom Branch Final Upgrade only works when vision exists)
  
• Flashbang

• Literally all of the above (Except Flashbangs)

• Flashbangs
  
• Guided Laser (An upgrade creates a vision field)
  
• Psych Trail (An upgrade makes trail emit vision)
  
• Charge Rounds (Charged boom makes vision area)
  
• Shield Barrier (Final Upgrade of top branch lights the whole field up in vision. Middle bottom branch makes vision circle visible in a small radius around player)

Yes it is. Lets count. There are 28 upgrade trees in the game currently. 14 either do not work in some capacity, or they directly nerf Concealed Fatigue. I'm not even sure if I caught them all, some missed may also negatively effect Concealed Fatigue in some way. That is half of the current upgrade roster. Unfortunately, many of the upgrades in the upgrades that negatively synergise with Concealed Fatigue are ridiculously good, especially because many synergise with each other. Meanwhile the ones that don't negatively effect Concealed Fatigue don't synergise at all with each other (Except for wildfire and burn... Electricity synergises with anything that doesn't kill in one hit) and especially do not synergise with Concealed Fatigue any better than with a vision build.

Surprisingly, only two upgrades make Concealed Fatigue a lost cause...

The two perks that make Concealed Fatigue not worth it. Light target works very similarly to top branch Concealed Fatigue, except it has bottom branch assisting its abilities even further. Light Target top branch makes enemies take increased damage when revealed in vision, as well as making enemies take less damage outside of vision, the antithesis of Concealed Fatigue's top branch damage buff and nerf. Bottom branch Light Target drops orbs that increase weapon stats, eventually giving increased vision radius and weapon stats with its final upgrade. It is also an antithesis of Concealed Fatigue's orbs, where they project a ring of bullets outwards from their point of origin, eventually lowering vision radius and increasing weapon stats. Unlike Concealed Fatigue, there is no downside of losing vision for this. The only advantage Concealed Fatigue has over Light Target is the massive increases to exp pickup range top branch provides.

Proximity Marker is the final reason why Concealed Fatigue is outshined by vision upgrades. Proximity marker has one downside: It is only a ring around the player and only effects enemies inside the ring. This ring can be increased as long as the player picks up vision increasing upgrades. With enough vision increasing upgrades, the range proximity marker can reach is impressive and negligible. The reason this upgrade tree is important is because 1. It increases the damage done to enemies inside its radius by a decent amount, and 2. It slows down enemies inside the radius by a decent amount. Both are invaluable when you get closer to endless mode. This pairing already outshines Concealed Fatigue's damage and slowdown, but without the sacrifices Concealed Fatigue demands.

There is none. Not anymore. Concealed Fatigue was an excellent sidegrade when damage buffs were limited. Boomerang Scythes, Saw Launcher, Twin Katanas, Greatsword, and Sniper Rifle were all super strong with it. They're still strong. But now they're more viable with vision then without simply because the damage buffs of Concealed are basically limited to a single perk, and those damage buffs continue to become more and more plentiful with each update.

Unless you're a challenge runner, Concealed Fatigue just isn't cutting it anymore.