Kill Switch update: Amanda's Letter add-on for The Pig has been Kill Switched due to an issue with incorrect RBT count.

http://dbd.game/killswitch

How could the killer ping issue be fixed?

Personally, I would simply make it to where if your ping isn't low enough, you cannot log into the game. This would effectively nerf lagswitching and make the game a little bit more playable.

Or, simply add ping based matchmaking.

You have low ping, get matched with other low ping players (with SBMM ofc)

You have high ping, get matched with other high ping players. And so on, and so on. However, it would be pretty stupid to say that DBD's servers are not slightly the problem. I would honestly improve the servers before anything else.