So, in essence, the top 500 players for the MVP rewards are going to be the folks who are both simultaneously luckier than everyone else and could clear the prior frontier dungeon then. That really just feels like a kick in the gonads.
I've come across both the jewel gods and winged mimics before, but I typically don't run with dark or light affiliated units, so I couldn't capitalize on it..
Most of these games that have a PvP/competitive element will reward the top/luckiest players and in effect keep them at the top.
It can be pretty frustrating, I try not to take it too seriously though, you have to work incredibly hard (AKA spend a lot of money) to maintain the top 100 let alone top place, which just isn't realistic for most of us.