This is a beta-note explanation. I haven't tested it in-game.
Why the older answers disagree
A 23 September discussion has players reporting conflicting results and asking whether the change worked for both Warriors and Bears. Those reports came before the relevant fix.
In its 8 October development notes, Blizzard said absorbed damage should be ignored when calculating Rage from incoming attacks, as though the Warrior or Druid had no absorb active. The same update addressed other Rage-calculation bugs. An older report of poor Rage generation isn't a reason to assume every shield still causes it.
Keep the question specific
That answer concerns a tank receiving an attack while shielded. It doesn't establish how much Rage a Warrior gets when attacking a shielded or immune enemy. Those are different interactions.
Paladins need a separate answer too. The later October beta notes say Power Word: Shield no longer overwrites Seal of Fury. That statement alone doesn't explain every interaction involving the seal's Mana return, Thorns or Retribution Aura. Don't turn it into a blanket promise about shielding every tank.
Before your next group
The Rage change removes one specific objection to shielding a Warrior or Bear. It doesn't make shielding on cooldown the right healing plan, or rank Priests against other healers.
If someone raises the old Rage warning, check which game version and update they're describing. If behaviour differs from the documented change, note the tank's class and form, the absorb involved and the current build rather than diagnosing it from a whole dungeon's pace.
For the broader preparation, the first-dungeon guide covers agreeing on the run before travelling.