This week's Mythic+ affix, Voidbound, is now much harder, but the reward has been massively increased as well!
This week's Mythic+ affix is Xal'atath's Bargain: Voidbound summons a Void Emissary which increases the damage reduction of nearby mobs by 10% every 3 seconds. On a +10 difficulty this Void Emissary only had 14 million and was easily cleavable, so much so that many players didn't focus it down.
It seems that this affix may have been too easy, as the affix has now been made harder and you'll definitely want to focus this thing down.
But with greater difficulty comes greater rewards!