just want to make sure I have this right:

Example:

Honored Librarian attacks a Helldrake (who has Flying keyword).

4 damage is assigned

Helldrake uses a shield card to shield 1 dmg, making the total now 3 assigned dmg

3 is divided by 2 (to 1.5) and rounded up to 2 before it is assigned (though after it is dealt).

2 dmg is dealt to the Helldrake.

The shield card did basically nothing, as 4 divided by two is 2 dmg.

It's the other way around:

Honored Librarian attacks a Helldrake (who has Flying keyword).

4 damage is assigned

4 is divided by 2 (to 2)

Helldrake uses a shield card to shield 1 dmg, making the total now 1 assigned dmg

1 dmg is dealt to the Helldrake.

Exactly as Khudzlin said.

First you declare the attack to the Flying unit. Since it's Flying, you divide (rounding up) the damage when you assign it. After the damage is assigned, you declare the use of the Shield(s).

Nice clear up for any starter, did this topic allready has it's sticky FAQ? Should be good to be there since we have more to worry about now and the Core has been around for a while now.

Nice clear up for any starter, did this topic allready has it's sticky FAQ?

Nope. It's addressed directly in the definition for Flying in the RRG's Glossary, p. 7:

"When a unit with the Flying keyword is attacked by a unit that does not have the Flying keyword, halve the damage that is dealt before it is assigned . If the resultant damage would be a fractional value, round up."

Nice clear up for any starter, did this topic allready has it's sticky FAQ?

Nope. It's addressed directly in the definition for Flying in the RRG's Glossary, p. 7:

"When a unit with the Flying keyword is attacked by a unit that does not have the Flying keyword, halve the damage that is dealt before it is assigned . If the resultant damage would be a fractional value, round up."

Ah excellent thanks for pointing that out aswell.