To be honest, 540 is the absolute minumum people should aim close for because other stats become more useful after hitting said number.
To put it simply, 540 makes your character basically crit-proof in "normal" situational hits. There are fights that take this off from you but there's reasons why.
You're better off finding a balance for Stamina and Avoidance stacking. Otherwise, minute increases in avoidance is what you stand to get from Defence stacking.
Healing is the source of life. Without it, you're left with death.