I have not used my 2stone in months, so my memory may be off. If I do recall correctly, I always had success with the stone around 700 or so (or less). If I went higher, near 800 or more, the bottom burned well before the top was done.
I typically mixed Caputo and KABF (or a higher gluten flour), 50/50.
Your experience looked the same, although perhaps for different reason than mine.
Best of luck,