Ghostface and Myers shouldn't be that weak
When i hear people complaining about those two, its always about how their insta-down don't mean anything against looping. But after playing them a bit, i don't think that their insta-downs mechanics are the problem that make them weak: it is more the restrictions applied to those insta-downs that make them weak in my opinion. Why does Myers have a stalk limit? Why does hitting a survivor with ghostface makes the stalk go away? Maybe if that would be changed, then those killers might be good against decent survivors.
Comments
Myers's weaknesses are his early game/how difficult it can be sometimes to get out of tier 1 if you're noticed early and obviously that he is an M1 killer. That said, while he's not by any means the best, I don't think he's as bad as people say. I don't really have much of a problem with the stalk limit personally, although I wouldn't mind if it were increased a tiny bit.
Beyond that, the main things I would really want to change about Myers would be reducing time to get out of tier 1 and increasing tier 1 movement speed to 110, along with some more addon changes (buffs/reworks to weaker addons and nerf tombstone piece). I've also seen people suggest faster pallet breaking in tier 3, but I don't want to fully suggest this yet as I'm not sure how balanced that would be as he already has faster vaulting.
Ghostface has a lot more problems. His power recovery is simply too long without addons/even with the recent update you're still heavily encouraged to run double recovery (it doesn't help most of his other addons are trash). And during that time you're just a pure M1 killer with a full 32 meter TR. Against good survivors who are paying attention it can be difficult to get a full stalk off, or even if you do, that gives them time to get to a loop and you potentially get nothing vs. you could have just M1'd and gotten an injure (in other words, stalking often isn't worth it/it is at least somewhat reliant on the survivor not noticing you). COH existing also made him a lot weaker for obvious reasons (hit and run isn't viable) but that's not really a problem with ghostface, that's a problem with COH. He's also heavily map-reliant.
As for what you mentioned regarding losing stalk progress on M1, it might be cool if it only regressed a specific amount (eg. 50%) rather than all of it, kinda like how trickster's laceration works.
I agree that Myers isn't that weak... especially with some add-ons. Making Myers a 110% while in tier 1, and make it last less, looks like a good idea to me too. I don't think his tier 3 is bad, i've only felt a real problem with how much fast you're out of stalk on someone.
Ghostface definitely has bad add-ons. There is none that creates any mechanic for him to work with. It might be redundant, but i'd like some aura-reading on survivors and gens while he's cloaked. I think people want Ghostface to cloak like Wraith... but i don't think its a good idea.