Yes, but you can have the best tank in the world, if you spam Medica II + Divine Seal + Regen + Cure III you'll get aggro, no matter how hard the tank can flash. He's not god.
The healers have to care about party's HP and aggro.
I really hate people talking without knowing, just saying random bullshit they think.
And I suggest to use Shroud of Saints only when you get aggroed by more than 2 mobs, so that you can reduce significantly your aggro in a dangerous moment.
But I never use Shroud or Regen, maybe sometimes Shroud on the adds of the enhanced Colossus in CM.