2pt14, 2pt15, 517ilevel, echo, EB (everything same as few posts above)
solo : 126 663 dps
multi : 130 248 dps
damage on main target when multidoting : 123 595 dps
edit : tried looking a bit more into simC, and it appears that in both "mutidoting" simulations I was a bit too "conservative" on the "wait till FS wears out on the 2nd target before reapplying", which meant "only" 180% uptime on flame shock in both case (178% and 179%). Adding the "you might also refresh FS if there is less than one tick worth of it on the secondary target (ie try to use dot clipping)" pushed FS uptime to 190%, added ~+500dps but -200 dps on main target.
(I replaced the line I added
actions.single+=/flame_shock,cycle_targets=1,if=!ticking&active_enemies<3
with :
actions.single+=/flame_shock,cycle_targets=1,if=remains<cooldown+action.flame_shock.tick_time&active_enemie s<3
)