To be honest, I think they should, especially in AoE settings. Bloodwhetting gets comically overrated around here due to its absurdity in dungeons but even it's still ridiculous how much healing you can do as a tank nowadays. It wouldn't be a problem if the fights justified it. As a tank, I like the idea of being able to keep myself alive but it should feel necessary not a way to invalidate healers. Sure, Bloodwhetting or Corundum isn't going to save you from Hephaistos' double autos but it does make it so a single Tetra or Druochloe will be more than enough.
All in all, it's a combination of things. Tanks have far too much self sustain, healers have far too many oGCDs and bosses aren't doing enough damage. Everything should be looked at come 7.0.