Lol.
Phoenix fire is the perfect, simplest, easiest, least lagging solution.
Set initial damage to whatever you want, damage per second to 0, AoE to something like 150-200, the cooldown should be something very small 0.03-0.04. I think duration does not matter. Or maybe it does - I will explain below.
Because only initial damage is more than 0, units will be damaged only once per the duration.
In addition to this, changing the missile art of the PF ability, will enable effects to appear at the units you pass through.
And yes, since the range of the PF ability can be(and should be) more than the collisions size of the unit, any unit standing near enough to the casting unit will be damaged too.
P.s. I really think sukuchi is done with a PF based ability.