In the game health only costs half as much as other stats (you get twice the health on artifacts and you get twice the amount of health on initial stat distribution).
You also must have twice the amount of health compared to your second highest stat for it to be considered the strongest stat when it comes to breeding.
The problem is that gene strength allocated in health only increases it by 1 point. As soon as you get additional gene strength from high gene strength parents two of the other stats will start to “catch up” to health because the highest gene strength stat does not grow twice as fast as the second highest gene strength stat). This means a stat other than health will eventually become the highest stat compared to health/2 and eventually health will drop to third highest.
My suggestion would be to treat health from gene strength like other health sources and a +1 gene strength in health increases health by 2 points.