I use Naramon Focus school for the "Power Spike" (Melee Combo Counter now decays while out of combat by 20 / 15 / 10 / 5 every few seconds, instead of depleting completely) to keep my combo counter up.
For your companion, [Helios] or [Helios Prime] will allow you to equip the [Deconstructor] or [Deconstructor Prime]. These companion weapons allow you to equip the melee mods, [Gladiator Vice], [Gladiator Might], and [Gladiator Rush] that will add, via the set bonus, an additional 30% critical chance per combo multiplier.
The [Daikyu] will also make a great pair, just as with any [Nikana], as it gives +3% life steal to your [Nikana] Zaw attacks while using the [Amalgam Daikyu Target Acquired] mod.
The riven can be replaced with either [Drifting Contact] (if you will not be using Naramon Focus), a 90% elemental mod, or [Weeping Wounds] for a hybrid