Universally I think its better to balance by increasing health than increasing damage.

This is going to be twice as true for "boss fight mutants" otherwise its just going to be a bunch of people running away from it cuz it does too much damage.

I don't think 1,000-2,000hp is a unreasonable amount of health if the damage of the creature isn't also unreasonable.

Like a max regular bear I don't think should do anymore than 40 damage, thats enough to 2-3 hit most people you would expect to solo it, so fighting it in pairs would be smart for alot of people still.

At this damage point you leave the ability to have a +25% damage mutant, that has massively more health.

So lets roll through some base creature rates and than turn them into mutants.

Hamster 15-30hp 1-3 damage
Chicken 15-30hp 1-3 damage
Douglas Squirrel 20-40hp 1-5 damage
Ground Squirrel 20-40hp 1-5 damage
Rabbit 30-60hps 3-6 damage
Rat 40-70hps 4-7 damage
Marmot 45-85hps 5-10 damage
Pine Marten 55-100hps 6-12 damage
Cats 60-120hps 6-14 damage
Dogs 70-150hps 7-16 damage
Raccoon 85-180hps 10-18 damage
Mule Deer 100-400hps 12-30 damage

So this means the weakest mule deer is going to be as strong as a max pine martin. This also means that the weakest dog at 70hp is as strong as a max rat at 70hp, they both have 12 damage and same hps.

I think "THIS" type of balancing would really help new players estimate what they are actually fighting, they can look at their health and know "okay this is roughly how strong its going to be" regardless of what they are fighting.

Now these last two are a bit of a different subject.

Coyote
Bear

I think coyote should be a stronger version of a dog AND that the raccoon should be WEAKER than the dog. I've seen alot of raccoons but I've never seen one bigger than a bluenose pitbull (that yours is modeled after).

So I think the tiers should look more like this with my proposed strength priority change;

Cats 60-120hps 6-14 damage
Raccoon 70-150hps 7-16 damage
Dogs 85-180hps 10-18 damage
Coyote 95-300hps 12-24 damage
Mule Deer 110-400hps 13-30 damage
Bears 150-500hps 16-40 damage