Collision damage, ie: getting stomped, smacked, launched, etc into walls 1 hit k.o. I once had 4x resist with Omnioculus while invis, and 100 resilience, Gahlran jumped into me and I was launched into a wall and died. I wouldn't even mind being able to survive with 1-10hp from collision without spec'ing into dmg resist. Also not sure if there are any mods or any ways beside blocking with a sword that would negate some collision damage.
Bungie's trolling antics are baked into the engine. They'd have to rebuild everything from scratch.