The natural healing rate in this game is extremely high, and as it has saved me many times I can't complain too much, but when I'm bleeding or lightly poisoned and it has literally no effect because my natural healing rate counters it, I believe it makes these effects almost negligible except when they are hugely stacked.
I was thinking a lower rate of healing (or slower rate of natural healing) might be a quick fix, but had another thought recently that I thought might "fix" the strength of natural healing.
When someone is bleeding, poisoned or under any effect that deals damage over time, the natural healing rate could be removed completely. Now this might make bleeding effects much worse in general, but they probably should be highly detrimental in effect considering.
If this were done, the damage rates of poison and bleed would likely have to be re-assessed and lessened in general, but to me it seems weird that in combat after being shot several times, one is still able to regenerate mysteriously well, even though we are supposed to be humans

Just another thought anyway.