Unfortunately with the item that can add mythic effects to all versions of tier, some classes favor the LFR tier looks over Normal/Heroic/Mythic so this is going to happen a lot and I see no problem with it. If it was personal loot, you woulda just asked them for it and they would have said no and you’d still be upset.
The issue with one person winning 3 identical pieces and not handing them out is something that should be addressed however. There could be many reasons why they didn’t hand them out - left group before they realized it, social anxiety and didn’t want to conversate to hand them out, had an emergency and had to go as soon as the boss was down, or perhaps they’re just a jerk or maybe even queued with friends and traded with them. Doesn’t matter the reason I guess, one person shouldn’t win 3 loots off one boss regardless and personal loot did handle that issue.
I really like the group loot change though (even with its flaws) so maybe a sound compromise would be to just make LFR personal loot and all other difficulties group loot. I’d also like to see bonus rolls return with group loot which could lessen (but not fix) some of the pain points with the system.