There is no problem with the numbers, the numbers are perfectly fine each game.
The problem is the 4% missing health healing.
Second Wind: After taking damage from an enemy champion heal for 4% of your missing health +6 over 10 seconds.
So If I'm missing 200 HP this rune heals me for 14 hp total in 10 seconds, which is a very long time...
I can even not take this rune, replace it with 'Conditioning' and not notice any difference in regeneration.
Because this rune heals on % HP you would think it would be useful late game but it does **absolutely nothing**, no impact simply because it heals based on missing health.
Basically it heals best when I'm pretty much dead or have to return to base, what's the logic in that?
Why 4% missing health and not 2% of my max health for example?
Just like 'Font of life' heals allies for 1% of my MAX health, 'Second Wind' should do the same.
If 'Font of life heals' for 1% max hp + 5, in 2 seconds.
'Second Wind' should heal me for 2% max hp +5, in 10 seconds.
Not only it does now what it's supposed to do, instead of healing me at full effect when I have to return to base, but also it's a useful rune late game which lets me regenerate poke damage.