barbarians can rage as a free action when rolling initiative

delaying means other classes can assist on doing even more damage (casters can buff the barbarian, debuff enemies, etc)

the whole point of playing barbarian (or any other tank class) is to be the easiest to damage (but also hardest to kill), so being "open to damage" doesn't really mean anything

actually, they'll be less open to damage since the enemies would need to waste actions to get close while the barbarian will be sitting still and will be able to use more useful actions and hit enemies instead of basically wasting actions by walking forward