I know this topic focuses directly on single target DPS but I can't see any other reasonable place to discuss this without making a new thread, would Ninja's AOE/Speedrun type rotation be something similar to this:

Doton > Kassatsu > Katon > Reapply Doton
Whilst inbetween the Ninjutsu using Death Blossom and OGCD skills and buffs.

This would be assuming that Kassatsu works as a critical only on the ninjutsu itself and not the DoT of Doton. I'm not sure on the recast time of Ninjutsu (20 seconds I think) so in that case would it be more beneficial to reapply Doton (30 potency over 24 seconds) instead of letting it drop and using Katon (180 potency) considering you would reapply the DoT when there is less than 2 seconds remaining, assuming the casting of Doton takes greater than 2 seconds.

OR would it be more efficient to open with Huton for the attack speed buff (though I would assume this could use to TP issues, does Huton directly affect GCD speed like Greased lightning?) then would it be better to follow that with Kassatsu Doton or Kassatsu Katon??