I think very end-game deadzones should be harsh environments similar to the Glowing Sea in Fallout 4 and other games featuring deadly radioactive areas. There should be far more deadly enemies in these areas, but greater rewards in loot. Everything from security systems (in some of the actual buildings within these deadzones, featuring hard to open doors or perhaps turrets), to bandits (maybe some deadzones could feature these bandits as end-game enemies rather than dealing with Turned), to horrible mutant Turned and wildlife (this oneās fairly simple and I donāt see why it wonāt happen).
Lower tier deadzones should rather be fairly normal, but have āambientā radiation, similar to how it currently is in 3.0.
I definitely think these deadzones should provide a challenging and risky experience with different enemy encounters, depending on location/map/the specific deadzone itself.