Except you needed bigger heals to get back to full, which might mean more heals or more inefficient heals. And in a world where mana matters, that's a problem.
In this scenario, lets assume you meant in default prior to choosing stam stacking or avoidance stacking it takes 12 hits. If you grab some avoidance, that means you have a high chance you'll at least avoid some of them, and thus give your healer a chance to heal you. (if you avoid at least once out of 12--although likely it's still possible to not avoid any) Now instead I opt to grab more HP, and low and behold, now i can take 14 or say 15 hits before death, same net result, healer has more time to heal me back to safe levels, and yet, there is no RNG (whoops didn't avoid any of the 12). That's why EH wins almost always. Because it is constant.