Blizzard really needs to fix this, this is the worst thing possible for rares.
Let’s take as an example Oily Invertebrate (10-10-10), which drops a quest starter item that rewards the appearance Pristine Containment Pack:
- low drop rate
- hard to summon
- able to be messed up by other players
It is hot garbage. You are close to making it, and then some clueless guy comes out of nowhere and starts throwing reds in, completely ruining. No matter if you are on your own or with a raid group, there will be 7/10 times this random guy ruins it (usually with the excuse of completing the daily quest, which only rewards 40 gold, at best). It is extremely hard to summon that way, it should be instanced or something. I have tried to do it many times, and I managed to do it only a few.
There is no way to do this. Just either make it instanced so you can summon it alone/with your group, or just leave it like that but boost the drop rates.