Indeed, considering the reward, the grind seems a bee wit out of balance.

It's also a bit strange that there are so many different chests, but perhaps it's for convenience so that you can do the areas in any order... but... still strange.

It would make more sense if we could open them each after getting the key for the area, and there's also this bug report [1] about confirming that which... they were unable to verify?

Did they not have access to Limbus or something?

I hope they will also re-add the Limbus RoE objectives so that people can still complete those, and also Omega and Ultima of course for the titles and such that the things those are required for will become available once more again.

1. Limbus Chest Requirements