I think they should change diadem to work like abyssea, where you work on pop items to pop larger NM's which allow you to pop the next tier and tier has its own drop table. Add the !! Triggers would be great also, I would also add the buffs you that you could buy but make it where you use GC seals to buy them. I'll even go as far as adding a way where if your GC control the area your cost of buffs is lower. But don't remove it revamp it the potential is there but SE is playing the safety first game.

I agree with everything else you wrote