Unless something was changed recently since I last played with Mutations, having Imperceptive Healer should not prevent you from getting Fast Healer - mutations often ping-pong back and forth between sides of a specific trait, you are probably just having bad luck.
It is possible that Mutagen isn’t enough, and you might require actual Serum, perhaps - but Fast Healer is a trait with no pre-requisites, so that is unlikely.
Are you going full Medical, or have you used other serums?
Would it be possible for you to post a screenshot of all the current mutations you have, please?
(Chances are that if you used other mutation lines serums you probably crossed a threshold in some variety. Which perhaps is what is causing you to not get the mutation you’re looking for. That or maybe some CBM interfering with it, although this latter statement is very speculative.).
I am almost entirely sure that Mutations that are on opposite ends of the same “line” spectrum (e.g.: tiny > TAANK!) and the “in-betweens” usually cancel eachothers out. Maybe something was changed that affects the “healer” part? Or maybe it was never the case for the “healer”-like traits due to an oversight or it being on purpose but never explained why.
uh if i rmbr, i have never gotten fast healer from medical mutation tree, i have gotten very quick pain recovery, try lizard mutation branch for fast healing, im also pretty sure cow, and plant have up to fast healer
I’ve done some debug testing with Plant and Lizard as well as other trees.
I will never get their healing traits. And as tested on other characters I made for this test, you can get Fast Healer properly IF you don’t have Imperceptive Healer as a starting trait. Having this stops you from ever developing Fast Healer.
This is kind of inconsistent since other mutations/traits that are on the opposite side of the spectrum cancel each other out even when chosen as starting traits. For all the healing related traits, they lack the property in the code to cancel each other out (like other traits). They are simply coded in such a way that they exclude other traits in Healing category from my conclusion. It just seems they are permanent compared to other mutations.
Can a dev confirm if this is intentional or is this an oversight?
UPDATE: I’ve done a few more tests and turns out Slow Healer can be cancelled, while Poor Healer and Imperceptive Healer cannot be cancelled by anything in the game, even the worse Healing mutations (Weakening, Deterioration, Disintegration).