"Edit: It seems that the Malefic Cores will only show up on MOTHER until you reach 89 Corruption Resistance at this time (not 92). Thanks to Cistara for pointing this out. "
This looks like bad timing with the purchasable cores coming out after the weekly reset, so that players may have already done the “normal” activities for getting a core.
I expect you’ll be able to use one of your purchased cores next week to upgrade to 92 and then can do a full clear or N’zoth kill for the new resistance cap. So I guess you’ll just have to wait a week, but you may wish to submit a ticket in case you need a refund for the cores?
You can still only upgrade your cloak 2 times a week (if you are behind). They did not increase it. So if you did the vision you can only upgrade it once. And if you did vision and nzoth you can’t upgrade it more.
They only did this for non pve players. Tho I like or for my alts that I don’t have to run nyalotha more then I want to. Would have been good if they increase the catch up to be unlimited or just by 2 extra.
I got the same problem, also did both vision & killed nzoth already… I don’t see why blizzard punishes those who put in the work before this hotfix to get the cores the usual way.