I plan to implement more infos on the API side. The people looking at it are smart and will help us out finding the values looking weird. Then why not graphing fancy things / tables on the website (that's Soak's part.)

But there is only ONE need that makes fancy stats like your idea (not exactly yours, I already see a way to do this the easy way) a nightmare for the developper : every miner can choose the difficulty of every of their workers.
A worker difficulty is not locked during the time. It can change from share to share.
So it is not possible to make stats globally on a given bunch of shares of a worker during a specific timeframe. You need to process each share individually before having something that looks good. On MariaDB's table with millions of rows, I'm sure you understand the problem.



Hypernova is currently handling ~3000 queries (including transactions) per second 24h/24 7/7.

So, nothing impossible but we need to do the things the right way !