If You Want Less Tunnelers, Add A Reason Not To Tunnel
I honestly don't think adding more perks or more ways for SURVIVORS to avoid tunneling is going to change anything. The biggest reason WHY tunneling is usually happening and the main priority for killers? There's literally no incentive to actually going for multiple hooks on multiple people.
There's no reason to, unless the team is quite clearly very bad and you can get away with it, all you're doing is wasting time and getting your gens blasted through if you're trying to go for hooks. It just doesn't work against good players.
If you want killers to tunnel less, add an actual reason for them to go for hooks on someone else. Why would I waste time to go for that full HP Nea who has zero hooks, if I can just go for the Feng who just got off the hook and is vulnerable. Why would I waste time for something that won't give me an advantage, if I can quickly get someone completely out of the game and will actually help me get some pressure.
It's less about tunneling being too strong and more about the fact that going for multiple hooks is too weak of a strat and just doesn't work. And this is coming from a guy that mostly plays terrible killers and still goes for hooks a majority of the time, or at least will full on leave hooks and try not to tunnel as much as possible. But if I feel like winning some day? I have to tunnel. Not because I want to, but it's because I HAVE to if I want to stay competitive and try to win, without getting completely washed.