To conclude what Evrik, Apollo and DangerousDiz had mentioned, there is another way to increase the threshold.
Turn off the instadeath, but set revivetimer to 5sec. You will still die af 5sec if you step on IED,hit by RPG or have multiple wounds. But you fall unconscious from the headshot or grenade. You can bleed out, it will depend of course how many wounds you got. At lest it was like that when i last time tested medical system 3 month ago.
If 3CB would agree to test this settings on public server for a limited period of time, that will provide necessary feedback.
P.S.
I am in both camps.
Instadeath off:
a. Some people become reckless, as you always have medic to fix you up even if you just stepped on an IED.
b. Slow down pace due to a.
c. Medics are crucial, skill matters. Experienced medic can tell which casualty go first and which can wait.
Instadeath on:
a. You know this feeling when you drive/fly 10min to AO and get killed with the first bullet.
b. Medics are not crucial any more, the section can hadle without the medic. Broken legs can be fixed with 9mm

.
c. You have to be very lucky/unlucky to live long enough that you will require medical assistance.