That's what ES is for, and why you never spec out of it. Vanguards often have the same issue, of no ranged in-place attack.
Or you could, you know, shoot things with a gun 
Ark171 totally rocks the Shadow on Platinum. It does, admittedly, help that he's totally batshit crazy because that's the only way to play her 
It takes crazy to know crazy, am I right? 
Sometimes you will need Martial Artist up and running to OHK basic units without relying on the DoT, if that's how you've built SS...but I'm pretty sure that's only Phantoms, Dragoons and Possessed Collector Captains on Gold and above.
And if you absolutely want to take those out without relying on DoT, well, just assassinate something else first.
I know you can OHK plat dragoons without martial artist or damage cloak or power amps - hydraulic joints does wonders for SS (no need to use that crutch scanner
)
I'm at work right now - also a phone, ughh - or I'd check specifics, but I'm pretty sure the only things that are safe (depending on sword evo) are the possessed troopers/captains...and maybe pyros, but I could see damage cloak/power amps being enough.
Shield/barrier sword should OHK plat phantoms depending on loadout, but you can always just heavy melee their asses with your sword after SS (they often flip) which should behead them