If the heroes are worried about dying and they should be in a Superworld type setting.
Let them buy extra hit points with a limitation only usable when hit points are below zero. or a small regeneration that has the limitation to only bring them back to zero. The limitation has got to be worth the max which is a 1/2
e.g.
"Hard to kill"
Power; Extra Hit Points; 5 levels; +10 Hit Points
Hero Point Cost; 5
Limitation; (1/2 points; Only to bring hit points back to zero) +3
So real hero point cost is 2
or
"Won't go down that easy"
Power; Regeneration; 1 level; 1 hit point per melee round; works on negative hit points
Hero Point Cost; 3
Limitation; (1/2 points; Only to bring hit points back to zero) +2
real hero point cost 1
Well worth the investment. If the situation is a worry for heroes then the solution is something they should spend hero points on.
At reasonable levels of earned experience earned hero points its cheap and also satisfying in the genre sense.
Cheers
M