"Reasonably slow but complete healthregeneration for everyone"
The title already sais basically everything.

[EDIT: YET ACHIVING THIS THROUGH THE PERK "BLESSED BLOOD" IS JUST AS FINE. EVEN THOUGH THAT WOULD REQUIRE A SECOND PERK SLOT FOR EVERYONE. OTHERWISE THE OTHER PERKS WOULD PROBABLY GO TO WASTE.]

Yet since i am pretty sure you already had this in mind, since it is technically already implemented in the form of the perk "Blessed Blood" the reason you refrained from just making it a passive for everyone to just have is probably your fear of its impact on the gameplay.

Now allow me to speak freely here for once:
THE IMPACT WOULD BE AWSOME! DO IT! JUST DO IT!!!
I mean sure there are other things, like just for example the fact that despite of the big "customize everything" shown in the trailer, I still can't add or remove helmets just simple helmets, which a LOT of people want by the way since a faceless guy can just be related to MUCH better. But you see I very well
understand that this kind of stuff takes time and work. And this brings me back to my original point. This is not such a thing. In comparison, it probably would be a few clicks on the right machine for you. But yeah, that is of course not even the big matter anyway. The big matter here is:
Do the potential advantages outweigh the risks.
I mean, I can imagine someone reading this thinking: "Well then why not just make every bullet oneshot aswell now that were at it, and increase the overall health to 10 times the current amount Ha-ha-hA-HA-HAA!" And sure, it is entirely possible to screw up the gameplay like this.
BUT "Reasonably slow but complete healthregeneration for everyone"
WILL MOST CERTANLY NOT!
IT WILL DO THE OPPOSITE

I love Deathwing, I love Warhammer, and I have great respect for you devs
because I know you do too.
So let me give specific reasons as to why
"Reasonably slow but complete healthregeneration for everyone"
should defenately be enabled.

1.This is not Vermintide. I am fairly sure that you took at least some inspiration from Vermintide when you guys first designed the overall gameplay system.
It was probably something like this:
In Vermintide there is no real healthregeneration, just some potions, some perks and bandages. So lets go a similar way in Deathwing but with an Apothecarius instead of the other stuff. And on paper, that doesn't sound so bad, but in reality, it is just not as good as it should be. In Vermintide, everyone is almost 100% responsilble for one's own health. That is the key difference.

2.You are absolutely dependant on your Apothecarius. Now sure ... you can go into a mission without one. But dooing so right now equals ruining the fun part of it completely. You see, every class in Deathwing is more or less equal at the moment. Good job on that devs. Every class with gigantic exeption of the Apothecarius, why? What makes him so special? Don't get me wrong, the Apothecarius is really awsome the way he is right now. Do not nerf him.
Enabeling "reasonably slow but complete healthregeneration for everyone" even includes him.
But it will make him equal and there is nothing wrong with that.

3.Now reading my last sentence "... nothing wrong with that." you maybe think of the scenario where a mission is launched without an Apothecarius, and whenever someone gets hurt he, or even the entire squad would just start to wait around for them to heal. Boring right? Yeah except for the fact that in 4of5 places you are beeing bombarded with Xenos. And even when you find a secure place, it is not even a bad thing to just wait a few moments to catch breath and regenerate. I mean, that is one of the reasons why psygates exist right? But the strongest thought that speaks against this fear is the following: It already is this way! Especially when someones legs get cripelled you have no other choice but to wait for the heal of the Apothecarius. Which he sometimes just doesn't care about because the Assults healthbar itself is often still not really down far.

4.Deathwing is a teamgame. No doubt. But why give away free possibilities?
I mean like 100% free. What I mean here is that, I for my part enjoyed it
incredibly much to just walk inside a mission alone. Not the campagin as there you are not really alone, but the multiplayer missions. But I never could do that with anything else than the Apothecarius. I honestly already fantasized about doing this with someone like the Assult like as if that was an unachivable dream. Yet it does not need to be at all. The only thing required to make it real is "Reasonably slow but complete healthregeneration for everyone".

Make it happen. S'il te plaît.

Maybe the perk ‘Blessed Blood’ should be a generic perk imo and available for everyone. Thus, if you want you can go slow health regen it’s a choice.

It seems wasted on the Apothcary coz he can just insta heal himself by waiting a brief time.

Blessed Blood as a Perk for everyone would be ok, but slow regen for everyone by default would be a shame. One more reason not to choose Apothecary and I guess even less teamplay.

Some of Apos perks make him fun, like ‘Chirurgeon’ and he’s got the ‘Hellfire’ n I suggested a new perk ‘Brain Surgeon’ which would make it fun for people to pop Tyranids’ heads off

I thot itd be good to have a valid way, tho no way as good as an Apo if it’s slow regen, to not have to have an Apo in one’s team and if you want it you’d need to sacrifice your perk slot for it. It could be good for some newer players and the lone wolves maybe?

Blessed Blood for everyone would also work. But I am sure almost everyone would use it then. EXCEPT FOR APO HAHAHA (Man ... giving it to him in the first place ... It is actually funny from a gameplay perspective).
Yet all the other perks would go to waste then. A solution would be a second perk slot in combination with giving 'Blessed Blood' to everyone.

... Hhhh ... it breaks my heart to see DWs steamrating down to mixed again ...
BUT DEVS! IF YOU READ THIS: KNOW THAT IT IS NOT TOO LATE!
BUT STOP HESITATING!

I'm not sure giving everyone health regen is a great idea. The game has already been built and balanced around the Apothecary being the only source for heals. Letting everyone regenerate slowly might mess stuff up.

Whether a Terminator could regen by themselves or not, an Apothecary would still be mandatory in harder difficulties because of how hard stuff hits you.

Blessed Blood for everyone would be just as fine, but it would reqire a second perk slot so it's no sad waste. And ofc a good Apo would still benefit the team greatly. But he would not be it's 100% cause of victory anymore. That's the entire idea.
And that's exactly what I adressed up there. It would SO not mess stuff up.

It would SO do if with a second perk slot. If people want that skill, there should be consequences... There are enough lone wolves destroying good matches with their running and smashing every door, we don't need to make it easier for them. If you dont wanna be Apo, just let someone else, there are even people, like me, maining the shit out of that class^^

Edit: It's "s'il vous plait" when talking to more than one person or someone you don't know properly

Then no second perk slot ... that was just a good advise.
But as long as "Blessed Blood" is given to everyone ... at least the bare minimum to save DW from its steamrating is done.

Edit: And I adressed only one person. For usually only one person is tasked with reading this stuff

... It is too late ... the people of steam have spoken. I tried what I can.
"This failure is yours and yours alone."

AND PS: Why the fuc are there still no helmets?!

I kind of wish the developers hadn't gone with the whole "healer" setup because it severely restricts freedom in squad selection, especially in single player special missions where there are only three members in your squad. Brother Nahum is little more than a walking medicine dispenser, most of which he is forced to use on himself because he's so squishy, so you effectively only have a choice between ranged and melee Brother Barachiel. It also restricts additional content: there will be issues in including other Space Marine chapters, because only the Deathwing regularly deploy Terminator Apothecaries.

I would have much preferred a regenerating health system (and a fast regeneration at that) with the Apothecary being more of a buffer and support class rather than essential, just like you don't absolutely have to bring a Tactical or Chaplain even though their rez is nice to have.

Horrible idea. Even though I rarely get to play the class I want (Assault) Because I have to always play an Apoth or Chaplain, but I think it would make the game silly if there was a regeneration for everyone.