Tomorrow took a while…
I had contemplated just responding to you with another data explorer query, but I agree the translation progress graph could do with an improvement and it is timely to do so.
Here’s a quick update on what we’ve done:
loading 
Cosmetic, but always nice
Cached timing and progress per content type
The loading time for this page is going to be very long because of posts. We already have a cache (2h), and will indicate as well. Since we also do more than posts and topics now, we show progress for them.
Per-locale breakdown for each content type
This level of detail is actually quite time-consuming to query for, and are details that don’t always need to be seen, so we only show them when the admin wants to see it.
This is now available, so just update your site and you should be all set.