>>529173412
The DR that armor grants is exponentially decreasing while enemy damage is exponentially increasing. So there's a pretty hard limit to how much you can tank via raw HP and armor values (and adaptation). The hardest content in the game (ETA) is still health tankable with a fair amount of effort but if you do endurance beyond that it becomes way way harder to keep tanking.
The best health tanking mod set are the Umbra mods and because of how Umbra polarities work they're both costly to add in terms of resources and in terms of opportunity cost.
Also I don't think DE has checked damage values on certain enemies since they were created so you'll be tanking fire from all around for tiny damage then get one shot because some off screen enemy did like 20x more damage than any other enemy and health tanking doesn't have a gate to prevent one shots.