Unbreakable should reduce recovery rate, not increase it.

I totally disagree. you would never be able to recover at before the killer was back. would make the perk totally useless in my eyes.

I don't think they need to do too much to Unbreakable. At the end of the day, it is pretty situational; if killer doesn't slug (or only briefly slugs to scare off altruistic teammates), then it can't be used.

However, I would be okay with it being treated more as a full "One and Done" perk. Ie, if a survivor healed themselves out of the Dying State using Unbreakable's effect, then the perk would completely deactivate (their recovery speed would revert to normal from that point forward).

Basically, this survivor could choose whether to wait for help (or a hook) and retain the enhanced recovery factor for later use, or they could save themselves for the sake of efficiency/convenience, but lose the benefits of this perk for the remainder of the Trial.

Unbreakable is rarely run without DS (in my experience, EU region on PC). It sees use in builds that already run DS because it guarantees that either your DS can be used or you can recover yourself and keep the DS for later. You are using half your perk slots to guarantee either your DS activates or you can recover with Unbreakable while the killer can't pick you up due to DS, and for the killer not picking someone up who might have DS active is generally the right play as that wastes more time of the survivor side than picking them up and getting stunned. Assume that the killer not being able to pick someone up because of a potential DS happens once per game (technically you get two chances for DS, after your first and second unhook each, but the killer won't always down you in the 60 seconds that DS is active after being unhooked).

In that case you are using two perk slots to activate one effect per game, either activating the DS to stun or using Unbreakable to recover (again, technically you can get both of these per game but that is rare, on average it should be roughly one of these effects per game). And that is still so strong that it is worth running. Using half your perk slots to activate an effect once per game is so strong that it's worth running. This would be okay if all the other survivor perks were so weak that they are not worth running, but that is not the case. I can list three good survivors perks which you can't all run in the same build as DS+Unbreakable because those two use up two of the three perk slots you would need: Iron Will, Spine Chill, any Exhaustion perk (this list not meant to be exhaustive, and the perks listed are not meant to represent the strongest perks survivors have, just perks with good effects). Each of those perks gives a good effect, but those effects are still worse than using two perk slots to get one other effect (DS stun or Unbreakable recovery once per game, see first paragraph). And that is a problem, that should show just how strong that one effect you can get off is.

DS is not only useful when you get tunnelled off a hook, DS enables you to go for awful plays, for example repairing a generator or opening a gate even though the killer is coming towards you, going for awful unhooks because the person you unhook can DS, and so can you if you get picked up instead, and so on.

At the same time DS is theoretically very easy to play around, as you just need to keep track of the time when a survivor was unhooked and when you want to pick them up check if a minute has passed, but that is such a boring and uninteresting counterplay that I don't think anyone really bothers with it. The exception to this being when two survivors are left, one is hooked, second survivor unhooks, you hook and kill that survivor, find the last survivor and then stand over them for a minute to ensure that the DS has definitely run out, which is super boring for everyone involved. The other option is to ignore a survivor that you have found because they might have DS active, but in that case the survivor can just get free time on a generator for example, or jump in a locker and force you to lose a bunch of time, or again, ignore them.

Lastly even if DS really only worked when the killer tunnels, and never outside of this situation, then you will still have DS active against a killer that doesn't tunnel all game if you survive until the gates are open and get unhooked. A killer get seven hooks in total, two on each survivor and one hook on the fourth survivor, which is a lot of hooks. The survivor that was hooked only once however still has DS. If that survivor then gets hooked with the gates open there is a very high chance of just outright securing an escape thanks to DS. If the killer had tunnelled during the game then the DS would be inactive and that survivor would be guarenteed to die. And that is a problem. DS is not just a perk that punished tunnelling killers but a perk that is just so generally strong that it is always worth running, when it appears that originally it was supposed to be a counter to specific situations.

just no