I think the new claiming system took everyone by surprise in 1.19

The original Problem
While killing a MOB... if other MOBs aggroed... and they died before the first MOB did, you would get ZERO credit for the kill... No loot... No XP.
This was especially stupid (that's not even exaggeration... It was pretty stupid) in leves.. which were open world instanced, the MOBs were yours and yours alone... and yet you could only "Attack the 1 red MOB!!!!!!"

What the community asked for? (I hate to use words like "we" when speaking only for myself... I know it's pretentious... but if it makes you feel better, the "we" can just refer to me and my LS)
The ability to claim multiple MOBs or at the very least.. get credit (XP and Loot) for killing MOBs that weren't claimed

What we got?
We actually got what we asked for but they also slid in the ability to attack MOBs claimed by others, even though I never saw anyone ask for this.

The problems it caused
1. Power-leveling was now possible because some high level character outside the party could slaughter everything for you.
2. Anything open world can now be super-zerged by as many people as you can muster. that was pretty much Yoshi saying he had no regard or serious plans for any open world NMs. You can zerg a stronghold with 40 people and clear it easily in minutes... but whats the ultimate reward? a "chance" at a cuirass that isn't worth using? Mask of the Mortal Hex?

Being Able to attack MOBs already claimed is one of the biggest things hurting this game. It works against the abolishment (I guess firefox doesn't think "Abolishment" is a word) of PLing and also against the idea of new open world NMs