The flower doesn't always drops. Also you need to get the MvP to have a chance to receive the flower. My GX friends usually get around 12-20 flowers a hour.
Used RK?
This is why it's a GX only event is what it feels on the other player base. If GX isn't going to be balanced out or other classes aren't going to be buffed than it just promotes everyone to play GX.
Also. GX doesn't even have to kill the boss. Let's take doppel who will fly away. GX starts on doppel and does 51% of his life in damage and it flies away. Someone else finishes the 49%. GX will get the MVP reward if he/she is anywhere on the map.