Have to agree on the new arena. It needs to open every 2-4hrs not the 8hrs currently. Guessing a lot of people are getting easy wins or impossible fights in the arena (only found out about this bug today when I had 5 walk throughs). As for the new crystals, they are a waste of time & space.
I have tried killing this final monster but even with over 6.5k GS I just get killed. Using the monk, my best and she just runs me over for 100% damage.