For a less expensive/serviceable build replace the riven (whose main purpose is to get crit chance as close to exactly 100% for Duplicate) with [Blood Rush] and Melee Duplicate with Melee Animosity, that build would be slightly better probably anyway. Not as cute and unconditional⁽ˡʸ ˡᵒᵛᵉᵈ⁾ though

For a fancier looking mod that does slightly less but will also cost you an extra forma use [Amalgam Organ Shatter] instead of [Organ Shatter]

If you want to use a primer you should replace [Primed Pressure Point] with [Condition Overload]

[Berserker Fury] would be better than [Quickening], but [Quickening] is more convenient for spontaneous meleeing; builds combo faster and actually works right away; However Primed Fury could be better if you want to spend an extra forma/your riven works better with it

Obviously this build would do around 4x the damage if you do use a primer (and [Condition Overload]), but even this is enough for even level cap stuff, so why bother yourself with having to switch weapons all the time? Spontaneous and convenient > technically better after a minute (lifetime) of buildup. Really it's just Tennokai carrying through anything that actually has hp, generates absurd slash procs and usually around 3-4 of them per strike, it doesn't even require viral status, and with [Primed Reach] and [Opportunity's Reach] it hits from almost 10m away
Also if you wanna use a different Tennokai use either [Dreamer's Wrath] or [Discipline's Merit], the rest just don't really work well (however i find that the attack speed + reaсh triggers tennokai more than enough to not really benefit much from these)

~28 slash procs per second with full Duplicate and no other buffs

[Jade] shadows added [Melee Elementalist], basically doubling the damage of this build, sort of makes up for the bonus hp the grineer now have.

Overframe currently doesnt allow me to put it on, but the new [Galvanized Elementalist] mod would be better than [Melee Elementalist] (slightly, and kinda worse if youre focusing on heavy attacks)