#Likely Rare The first benefit is an extremely situational version of the Cloak of Protection (minus the +1 to saving throws), an Uncommon item. Uncommon items are considered +1 items. However with the significant restriction that they attacker must have advantage, that you must not have just attacked them and the loss of the +1 to saves this ability is really only a Common. Hence unlikely to increase the rarity significantly.

The second benefit we have no precedent for, negating damage like that isn't something that commonly happens in 5e. If we were to consider it equivalent to imposing disadvantage on the attack roll* (a more sensible ability) then it would be the same as the Cloak of Displacement, a Rare item. Rare items are +2. The Cloak of Displacement has a limitation to only work until it is hit each round. This offsets some of the differences between disadvantage and 10% miss chance.

This damage reduction could also be considered equal to a +2 to AC. Increase AC by 2 also reduces incoming damage by 10% (sort of). +2 Armour is a Rare item. So either way this ability is roughly equivalent to a rare item.

The 1% chance of doubling damage is fairly insignificant and balances out with the first benefit. So in total this item is mostly likely Rare.

*10% Miss is slightly better at reducing damage at low AC < 10 and gets worse as AC increases. See this anydice calculation for the math.

Likely Rare

The first benefit is an extremely situational version of the Cloak of Protection (minus the +1 to saving throws), an Uncommon item. Uncommon items are considered +1 items. However with the significant restriction that they attacker must have advantage, that you must not have just attacked them and the loss of the +1 to saves this ability is really only a Common. Hence unlikely to increase the rarity significantly.

The second benefit we have no precedent for, negating damage like that isn't something that commonly happens in 5e. If we were to consider it equivalent to imposing disadvantage on the attack roll* (a more sensible ability) then it would be the same as the Cloak of Displacement, a Rare item. Rare items are +2. The Cloak of Displacement has a limitation to only work until it is hit each round. This offsets some of the differences between disadvantage and 10% miss chance.

This damage reduction could also be considered equal to a +2 to AC. Increase AC by 2 also reduces incoming damage by 10% (sort of). +2 Armour is a Rare item. So either way this ability is roughly equivalent to a rare item.

The 1% chance of doubling damage is fairly insignificant and balances out with the first benefit. So in total this item is mostly likely Rare.

*10% Miss is slightly better at reducing damage at low AC < 10 and gets worse as AC increases. See this anydice calculation for the math.

#Likely Rare The first benefit is an extremely situational version of the Cloak of Protection (minus the +1 to saving throws), an Uncommon item. Uncommon items are considered +1 items. However with the significant restriction that they attacker must have advantage, that you must not have just attacked them and the loss of the +1 to saves this ability is really only a Common. Hence unlikely to increase the rarity significantly.

The second benefit we have no precedent for, negating damage like that isn't something that commonly happens in 5e. If we were to consider it equivalent to imposing disadvantage on the attack roll* (a more sensible ability) then it would be the same as the Cloak of Displacement, a Rare item. Rare items are +2.

This damage reduction could also be considered equal to a +2 to AC. Increase AC by 2 also reduces incoming damage by 10% (sort of). +2 Armour is a Rare item.

The 1% chance of doubling damage is fairly insignificant and balances out with the first benefit. So in total this item is mostly likely Rare.

*10% Miss is slightly better at reducing damage at low AC < 10 and gets worse as AC increases. See this anydice calculation for the math.

#Likely Rare The first benefit is an extremely situational version of the Cloak of Protection (minus the +1 to saving throws), an Uncommon item. Uncommon items are considered +1 items. However with the significant restriction that they attacker must have advantage, that you must not have just attacked them and the loss of the +1 to saves this ability is really only a Common. Hence unlikely to increase the rarity significantly.

The second benefit we have no precedent for, negating damage like that isn't something that commonly happens in 5e. If we were to consider it equivalent to imposing disadvantage on the attack roll* (a more sensible ability) then it would be the same as the Cloak of Displacement, a Rare item. Rare items are +2. The Cloak of Displacement has a limitation to only work until it is hit each round. This offsets some of the differences between disadvantage and 10% miss chance.

This damage reduction could also be considered equal to a +2 to AC. Increase AC by 2 also reduces incoming damage by 10% (sort of). +2 Armour is a Rare item. So either way this ability is roughly equivalent to a rare item.

The 1% chance of doubling damage is fairly insignificant and balances out with the first benefit. So in total this item is mostly likely Rare.

*10% Miss is slightly better at reducing damage at low AC < 10 and gets worse as AC increases. See this anydice calculation for the math.

#Likely Very Rare, maybe Rare The first benefit is basically equivalent to the Cloak of Protection, an Uncommon item. Your facing rule makes this slightly weaker however magic items with combat bonuses don't exist below uncommon so it would still be the same rarity. Uncommon items are considered +1 items.

The second benefit we have no precedent for, negating damage like that isn't something that commonly happens in 5e. If we were to consider it equivalent to imposing disadvantage on the attack roll* (a more sensible ability) then it would be the same as the Cloak of Displacement, a Rare item. Rare items are +2.

Both these benefits together on a single item sum to a +3 or Very Rare item.

*10% Miss is slightly better at reducing damage at low AC < 10 and gets worse as AC increases. See this anydice calculation for the math.

Since 10% miss chance isn't quite as much of a damage reduction if you have a high AC as imposing disadvantage is, you may like to consider the second benefit only uncommon. In this case the total item rarity is Rare or +2.

#Likely Rare The first benefit is an extremely situational version of the Cloak of Protection (minus the +1 to saving throws), an Uncommon item. Uncommon items are considered +1 items. However with the significant restriction that they attacker must have advantage, that you must not have just attacked them and the loss of the +1 to saves this ability is really only a Common. Hence unlikely to increase the rarity significantly.

The second benefit we have no precedent for, negating damage like that isn't something that commonly happens in 5e. If we were to consider it equivalent to imposing disadvantage on the attack roll* (a more sensible ability) then it would be the same as the Cloak of Displacement, a Rare item. Rare items are +2.

This damage reduction could also be considered equal to a +2 to AC. Increase AC by 2 also reduces incoming damage by 10% (sort of). +2 Armour is a Rare item.

The 1% chance of doubling damage is fairly insignificant and balances out with the first benefit. So in total this item is mostly likely Rare.

*10% Miss is slightly better at reducing damage at low AC < 10 and gets worse as AC increases. See this anydice calculation for the math.