You need to make Health more valuable. Because Defense is a flat damage reduction, and it is perfectly possible to outscale enemy damage at every stage with every class, Defense is wildly more valuable than Health. To the point it is not worth putting Health higher than maybe 5%. The difference in value is just that big. Add a derivative stat to Health like passive HP regen or something that helps bring it more in-line with other stats, or maybe add skills that scale with Health.
Also, can I please get a "Sell All" button?