Uniques are not all of the same rarity
When an item is generated rarity is determined first, it can be white, magic, rare or 1 of some number of unique rarity bands. exactly how many tiers of unique there are has not been publicly revealed.
If the item is unique, a unique is chosen from the chosen unique tier.If the item is not unique, then base type etc is determined.
In the case of chancing, base type never needs to be determined. however if a unique tier is chosen for which no unique of that base exists, then the item defaults down to a rare. So the existence of multiple uniques for a base only affects the probabilities of getting those uniques if more than 1 is on the same tier list.
So to be clear, in a world where infernal mantle did not exist, the chances of getting shavs would remain the same. All that would happen is you would get a rare on those rolls where you would have gotten infernal mantle.

Oct
Patches, Updates, Build of the Week & More At Path of Exile
This week's Path of Exile: The Exiled Tribune is a good meaty one with news about forthcoming v2.4x patches and changes to the difficulty levels for the game with the arrival of v3.0 in 2017.

Jan
People saying that there is no P2W in Path of Exile are correct
no Poe hardcore player so if i did anything wrong dont bust my head for it. all i ever learned about the game in that few play was chromatic orb, didnt learn anything about regret.

Sep
poe4orbs:10 Minutes Delivery Guarantee will be added on poecurrencybuy.com
Poecurrencybuy delivery guys may not be able to finish the delivery for all orders within 10 minutes. In order to make those whose orders are not delivered in time feels better, so have decided to develop “Delivery Guarantee” function, this will let those who have waited for longer than 10 minutes get the compensation from us while not to have negative feelings to our site.

Dec
The Dancing Dervish(1200+ Str) - Path of Exile 3.1 Chieftain Marauder Build - War for the Atlas - Abyss League
Hey bros, I have fallen in love with Path of Exile now, yes, my friend recommend this game to me and it becomes my favorite mmo game now! I have spent hundreds of times to create an ultimate Chieftain Marauder Build and find fast way to farm orbs in Path of Exile.

Oct
This is my honest feedback - Path of Exile Designers
This game has a unique feel and it is not easy to offer a self contained and well defined experience nowadays. Path of Exile is grim, compelling and harsh, in a good way.