Lootshare Rampage!

Only got one quest done yesterday, but I did get to 90 strength. The goal will be the same today as it was yesterday.
The thing I really had a problem with yesterday....Lootshare Rampages! I was trying to finish up a Fire Giant slayer task in the Chaos Tunnels when two people decided that the Fire Giants were not mine to kill. Over and over again, they decided that it was more fun to kill the few on my side, instead of the 4-5 that were alive and well on the side they were at when I arrived. Only when the ones near me were dead would they go back to the other side, but as soon as they spawned again they would leave their side, and come runniung back to where I was.
This is an annoying habit that I run into too frequently. Why is it that people cannot leave you to something you attack, and kill something on their own? I see it while killing Tzhaars all the time! People just turn on LS, and run around killing only monsters that have already been attacked. I am not strong enough to outhit 2 people at certain high levels who act like they own the world.