So, what’s the problem? It works exactly as written: you need to defeat the normal version of the boss for this one.
Ah, the famous ‘annointed’ Bli$$ard™ spelling.
I’ve been making fun of it at every opportunity for quite some time, by the way, for exactly this reason.
Interestingly enough, the equipment was formerly bugged — one couldn’t obtain it at all, neither from the normal nor the ‘Heroic’ version of the boss, and the misspelling might have had something to do with it, I dunno, but that was my assumtion then, if memory serves. They have long fixed it, and you can, I believe, get the equipment as you are supposed to, but the ‘annoy-nted’ bit has remained (or returned? I don’t rightly remember) for the Heroic bounty.
PS For a quick reference:
https://www.youtube.com/watch?v=VJsc0Lt2K4w .
The official topic with patch info might be gone, as is often the case with various topics on these forums, unfortunately.
PPS 25.4 Known Issues — the linked topics about hotfixes are no longer there, https://hearthstone.wiki.gg/wiki/Patches doesn’t seem to contain those, either, so the video will do as a reference for now. Haven’t bothered to check some web archive, though, but do I need to?
PPPS Alright, found this: Mercs - Lilian Equipment - #13 by Trimutius-1631 .
Somehow, 25.4.2 Patch Notes (still a ‘dead’ link here) could be opened via that post (or can be, at this moment, from the quotation block below). 
Ah, these forums…
PPPPS Ugh, what an ‘arcaeology class’ this exercise has been! 