Riven Slot
Replace riven with [Gladiator Might]
Side note: the riven disposition is wrong on overframe for both the [Quassus] and [Quassus Prime]. The riven stats in game actually read slightly higher.

[Galvanized Reflex]
This new Galvanized melee mod makes it so that you [Reach] around 6x combo multiplier and are guaranteed to red crit on about 25% of the blades that come out of the heavy attack, making it extremely strong. If you have any other means of buffing your critical chance (Arcane Avenger, [Smoke Shadow], etc), you will likely guarantee red crits all the time.
A case could also be made for using [Relentless Combination] on this weapon, since the initial combo from [Galvanized Reflex] plus the amount of combo you build with relentless can also guarantee red crits. This would likely replace [Gladiator Might], and you would want to store the gladiator set mods on a sentinel weapon.

Arcanes
Melee Retaliation is really the only viable arcane for this weapon since Melee Duplicate doesn't proc on high tiers of crit, Melee Animosity does not proc because the bleed damage originates from the heavy attack, and Melee Afflictions does not proc even though enemies will get knocked down by subsequent heavy blade hits (though this is likely a bug?).
You can use Melee Influence really effectively if you can outsource the electricity proc. This can be achieved through [Lavos]' [Valence Formation], [Volt]'s [Shock Trooper], or [Gyre]'s [Conductive Sphere].