144 Mikhail 8 minute HT solo

Your argument was that using a variety of demon slayer skills would reduce dps, yet spamming assassinate is the best 1v1 dps for shadowers.

I'd advise you to look at the skills that JoeTang has listed that are used for Shadower DPS.
It's Edge Carnival, Boomerang Step, Assassinate when 5 KP are accumulated, and Meso Explosion before the mesos disappear.
That is to say, NOT spamming assassinate.
This is a post-justice conversation not a pre-justice conversation, as you should have been able to see from the start.