This thread was so promising. Anyway, as a long time endgame healer and on-the-side tank, it's pretty clear to me that know competent healer would let a tank sit under their maximum health in any sort of mildly challenging content, whether that tank has a billion hitpoints or a couple thousand. Once you're not using endurance, it's useless and you could stack ANYTHING and be more useful (alacrity for faster TK throws, lol?). Of course, stacking actually tanking stats is best, but if that's not an option, no reason no to take the willpower option.