Yeh, could we make it so tethers can be dodged
You used to be able to dodge fizz ult with

Now, all tethers go through dodges/invulnerable
You used to be able to dodge fizz ult with

Now, all tethers go through dodges/invulnerable
These champions become untargetable, not invulnerable. If the tether/baby fish for shark/DoT is on you, you still take damage. Working as intended.
The tether works as a distance dependant dot. It's already applied to you, so as long as you're not out of range it will continue to tick. You don't dodge dots, so why dodge tethers?
fizz ult isn't a tether