If you want more damage output, max double first.
We don't know for sure, but we assume that 100 dbl/trpl buff doubles the chance of doing that stuff. Because base double is 8% and triple is 3%, it is assumed that double is better than triple (since 16% double is stronger than 6% triple). Nobody has bothered checking though.Correct.
Still, many use it just for Burst Hour shenanigans. If you want to push during 2/24 hours, then Burst is still the best stat after Atk. That said, even then you probably shouldn't use past 66/67, since that's where you hit the cap with Provisional Forest.
So, for damage output:
Atk > burst (for Burst Hour only, and drops in significance at high Demon levels) > dbl > trpl > burst