Tim,
GH 4.1 should ameliorate the chart rendering time.
Can you let me know if you see any improvements on this?
4.1 will be release the 2nd of November.
Since we need to parse all issue histories to compute the charts, the next step would be take advantage of the JQL support of the History and Worklogs when it will be implemented.
I will transfer this is the blocked issues until the JQL gets enhanced.
Cheers,
JC
The computed data the Hour Burndown Chart is based on is now cached in memory.