By the time a PC can just shrug off 70 damage (not just survive it), they're high enough level that they're well into the heroic tier of adventures, and superhuman feats like that shouldn't be beyond them.

I disagree, my barbarian had nearly 100 HP at level 6.

I never rolled lower than a 9 and got quiet a lot of double digits, just call them all 10's for easy of reference for HP from 2-6

12 + 10 + 10 + 10 + 10 + 10 = 62

con of 20 = + 25 = 87

tough + 10

= 97 (Was some where around that)

Of course I rolled for stats and put my 18 in con and went dwarve then got the toughness feat that adds 2 hp per level.

So second tier if you roll well can be just go "Lol climbing down, I'mma rage before I hit the ground. See you guys at the bottom in an hour!"

Not likely to happen, but god it feels great to be an HP bag when the stars align.