Its survival of the fittest, if you dont adapt to the powerbuild rules, you will easily die. Also I dont agree that powerbuilds have low INT, almost every powerbuild uses BROF, which requires 6 int, thus everyone sets INT to 6.
With current mechanics, lvl 12 lifegiver gives a 4 END char almost 50% hp boost, 10 END char receives 25% boost. As long as we have low maximum hp, we need to take lifegiver (speaking about combat chars). If you want to nerf lifegivers, you need to raise hp pool.