I go the same thing lol and was told “Our Developers have fixed the issue that was causing this bug, but we are getting some new reports about it, so they are currently investigating it again. At this time, we do not have an ETA on a fix. Game Masters are unable to grant credit for individual bosses for this quest. If you are still missing credit for some, please be sure to submit a new bug report so that our Devs can continue to investigate.” and “Keep in mind, you need to kill 30 different bosses, so you can’t kill the same bosses on different difficulties, or they won’t count. If you killed a boss before the hotfix, and you still didn’t get credit for it, try killing that boss again. You won’t be able to loot it again this week, but it may grant the credit”
I hope this means they will reset the boss kills again or something before next reset.
I have reported this as a bug in game with a link to this thread. So hopefully they see it and are working on a fix.
That helps, hopefully.
EDIT:
Went back into the wing with Lady Darkvein (the boss I think 99% I did not get credit) and touched the console; orb went down, touched it again to make the orb pop up.
Killed Huntsman, didn’t die and got credit.
No idea if this will work for others but thought it’s worth a mention.
Same with me here, hopefully the bug gets fixed soon.
I had to redo the first 2 LFR wings that I noticed that did not give credit, and it worked, got 1 kill credit from each
Not ideal but it worked 
Confirmed - Still bugged - Just did 10/10 for raid bosses, only got credit for 9/10.
Died on Denathrus, got raid boss kill in LFR - Did not count towards Fated Quest.
Yes, I found this out but was happy to obtain a higher ilvl pc of gear dropped so that at least is a consideration.
While Castle Nathria is Fated this week, the Revendreth world boss Nurgash Muckformed will also drop ivll 285 loot!
I am also experiencing this issue. Got the achievement for Castle Nathria this week on new alt with 10 bosses dead, but only have quest credit for 8 bosses. I know Sludgefist did not count.
Still having problem! today(08/07/2022 01:27 Brazilian time), I killed 10 locator bosses and counted only 8 for the mission!
I did 10 bosses, but got 9/30. Help!!!
I’ve done LFR twice now and still stuck at 9/30 instead of 10/30.
I did a full clear on 7 different characters (yes I have no life) and only got full credit on 2 of them. I tried the oribos relog thing, no luck on any of them.
You all are not alone. Several folks I ran LFR with last night experienced the same fights and earned the kills, but 1 out of 3 did not get full credit.
I suggest submitting tickets on this as it appears to be more widespread than we originally thought when our group discussed it.
I personally killed 9, but got credit only for 6 on my shaman and realized because I did 3 on LFR w/her, then went in on Friday and did normal up to the dance floor group (which we will start on Monday), I had forgotten my first three LFR kills on my shaman counted and I got no credit redoing those same bosses on normal.
So if you did LFR then went in to do normal or higher, you will only get credit for the first kill of any boss you fight no matter the level.
But that still does not account for the discrepancy if you did not actually get the credit for those first kills. I would say Bliz has a problem to fix on this.
7 bosses kill today (sat 8-7-22) only 6 credited. standing in Oribos, logged in and out several times. Started with Sire if that matters.
I’ve killed 10/10, including some re-kills…and I’m stuck at 9/10. This really needs to be fixed.
I’m at 9/10 heroic fated and only got 8 kills on the quest.
Had a disconnection issue after Kael kill and not only that fight was not registered, the achievement tracking is also not completed for Kael, but my Adventure Guide marks Kael as killed and looted.
Yeah this issue happened to me this week too. I killed all 10 bosses on LFR on this character and only got credit for 9. Kael’thas was the fight that didn’t give credit for me. I submitted a support ticket with screenshots and info to hopefully get credit for it.
I’m glad I’m at least not alone here.
Just did a full LFR run with my gf, I’m 10/10 she is 8/10. Really frustrating.
I just did a full run and received 9/10 credit for killing all bosses? What gives??