"Health link", "Shielding" and damage reduction

Question

As we now, elite monsters with the "Health Link" skill share part of the damage they receive with the rest of the monsters in their group.

Then there is also the "Shielding" skill, which makes the monsters immune to all damage for a short period of time.

With these two concepts clear, I have the following questions:

1. What happens if a monster shielding itself (and with the "Health Link") is attacked? Will all damage (for all monsters) ignored or will only that monster not receive damage?
2. If a monster with the "Health Link" skill receives damage and sends part of it to another one protecting himself with a shield, will this second monster receive any damage? Will it be shared at all?

In a similar fashion, the "Blood Clan Sorcerers" have the ability to cast a damage reduction shield. If a pack of these monsters has the "Health Link" skill and, say, all of them have a damage reduction shield except for one...

3. Does it make a difference which monster you attack? If you attack a protected monster, will all the damage get reduced and then shared or the other way round?.

EDIT: As fbueckert and Adeese correctly mention, "Health Link" and "Shielding" cannot appear together in the same pack. The question about the "blood Clan Sorcerers", however, remains valid.

Answer 1

According to a blue post on the D3 forums, Shielding and Health Link are both in the Defensive category, and there is a limit of 1 defensive ability per elite pack.

The relevant section:

"Defensive" (Limit 1):
  - Avenger
  - Extra Health
  - Health Link
  - Horde
  - Illusionist
  - Missile Dampening
  - Invulnerable Minions
  - Shielding
  - Vampiric

As you said, the 1.0.4 patch notes modified the behavior slightly, with the following points:

  - Jailer can now no longer appear with Knockback, Nightmarish, or Vortex
  - Invulnerable Minions has been removed as a possible affix

There's no mention of modifying the original affix category limitations, though, so I believe it has not been changed. The only one that impacts the defensive category is that Invulnerable Minions no longer available.

To that end, your question is a moot point; it's not possible for elites to spawn with both Health Link and Shielding.

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To answer the secondary question requires a basic understanding of how Health Link works.

It essentially divides the incoming damage to spread it out between itself and its friends. So if there are three of them, and you're only hitting one, you're doing only a third of your regular damage to that monster. But in exchange, the two monsters you aren't hitting are also taking equal amounts of damage. Things get a little wonky with AoE attacks, but the basic gist is, damage is divided as equally as possible, as long as they're within range.

With that in mind, any abilities affecting targeted monsters that reduce incoming damage will come into play prior to Health Link. If you hit a monster that has a shield, and Health Link, only the reduced damage will be linked. On the flip side, though, if you hammer his buddy, and he doesn't have a shield, then Mr. I Take Less Damage will take equal amounts of damage as his unshielded buddy. This is because the shield reduces incoming damage, and Health Link doesn't do damage; it just splits damage done between its members, essentially bypassing the shield entirely.