If someone has the key and has risk defence on, you CAN still attack them. The only instance I can see risk defence being a burden for key hunters is when the person attacking the key holder has risk defence, and you lack the risk to hit them off. That is your fault for showing up to a profitable and competitive event with a 0pkp setup.
I understand that large CC’s having dominance over the key can be frustrating for single pkers, but that’s just how the game is. With the recent addition of a brew cap, I don’t see anything wrong with the wilderness keys.