When people do this to me I switch to blm and deliberately -ja their mobs once they're down far enough that i can kill in 1 shot. Yes mobs u don't have claim on are technically not your mobs, but you don't go around in a grocery store taking things out of other people's carts do you?
Anyways, the people who do this on Lakshmi are 95% of the time RMT who charge people to sit there afk while they cleave for hours on end. That's even more incentive to steal their mobs. Yes legitimate players probably paid them, but boo hoo. They know it's an RMT doing it and they don't care as long as they can get leveled while they sleep. It's almost the same thing as paying cash for power leveling services.
+1 totally agree.
I refuse to pay to get exp which is so easy to do anyway, dont know about anyone else but Sylph sometimes has Key issues because everyone wants to play their jobs instead of just being a "Key Master".
As for the OP my heart goes to you but sadly this happens, all you can do is carry on taking a mob here and there - pop times are not exactly short so you should be okay. I would get in to the arguement of stupid FC parties but no point if people are prepared to pay for the very thing thats easy to get then hey ho.
If my velocity starts to make you sweat, then just don't