I'm going to leave a shadow copy on GD to grab attention.
I notice this might seem minor, but I'm afraid high level perks will really make this "Overpowered" (OP)
Basically, you can have two perks at once. One is Healthy Boost, and it always will be. The other can be anything else. I've tried it 3 times, it always works.
How to replicate:
If you haven't already, select healthy boost perk. You must restart the level you are doing or change just one piece of armor or a weapon for it to take effect. After it has taken effect, switch back into whatever armor you WANT to run the level with. When that's done, just pick any perk- it can be damage bonus (most noticeable) or defense boost or whatever. Then run the level. You'll keep the extra health and the perk you chose.
Why it works: Healthy boost does not give health to you in real time for some reason. You must change a single piece of item in your loadout- It can be an armor, shield, trinket or weapon- before it takes effect, be it actually adding health or reducing it.
Please fix this.
Although I never thought about using it to my advantage ;)
Good Catch!