So Esteemed leader in play and B2 droids are used as Guardian

Would their armour 1 take effect?

No.

"While a friendly trooper unit at range 1 and in line of sight is defending against a ranged attack, a unit that has the guardian x keyword may cancel up to x hit (󲉠) results. For each hit (󲉠) result canceled, the unit with the guardian x keyword rolls a defense die matching its defense." Edit: "A unit that uses guardian x to cancel hit (󲉠) results is not a defender and does not gain suppression tokens."

Guardian page 44.

"During the “Modify Attack Dice” step of an attack, if the defender has the armor x keyword..."

Armor X page 15

The B2s are not the defending unit, and Guardian is not worded to allow for Armor to apply regardless.

Cool , the armour quote clarifies any disputes

It's for the same reason that the guarding unit cannot spend dodge tokens (unless having Soresu Mastery which allows it to spend 1 dodge token). The Armor and Dodge apply in a different step, before the Guardian triggers.

1 hour ago, Lemmiwinks86 said:

It's for the same reason that the guarding unit cannot spend dodge tokens (unless having Soresu Mastery which allows it to spend 1 dodge token). The Armor and Dodge apply in a different step, before the Guardian triggers.

No, they (Edit: Armor applies) in the same step "Modify Attack Dice." The wording of Guardian doesn't allow for Armor or Dodge to apply, you have to be the defender to use either of those rules. If your unit is taking hits due to using Guardian to "protect" another unit, then it isn't the defender.

48 minutes ago, Caimheul1313 said:

No, they apply in the same step "Modify Attack Dice." The wording of Guardian doesn't allow for Armor or Dodge to apply, you have to be the defender to use either of those key words. If your unit is taking hits due to using Guardian to "protect" another unit, then it isn't the defender.

You're right, Armor applies during the "Modify Attack Dice", I was confused about that one. But dodge do apply before as it's used during the "Apply Dodge and Cover" step, which is before the "Modify Attack Dice" step. Even so, it wouldn't apply because, as you said, the guardian unit is not the defender.

9 minutes ago, Lemmiwinks86 said:

You're right, Armor applies during the "Modify Attack Dice", I was confused about that one. But dodge do apply before as it's used during the "Apply Dodge and Cover" step, which is before the "Modify Attack Dice" step. Even so, it wouldn't apply because, as you said, the guardian unit is not the defender.

Right, I forgot Dodge/Cover were an earlier step. I should have remembered because of the interaction between Dodge and Impact.