Yes, this is a bit funny looking. Let me explain.

[Elemental Sandstorm] looks exclusively at the weighting of damage types on your melee weapon to decide what status effect it applies per damage instance. Basically, you can have a very silly looking melee weapon, like this [Serro], and achieve the same (or higher) [Elemental Sandstorm] effectiveness as a traditionally modded melee weapon, you know, one that you might actually use to kill stuff.

Basically, [Serro] is what I consider the ideal weapon for this kind of [Inaros] build (at least for this mix of elements). It only innately deals Slash and Electric, easily letting you mod for Viral as well. The weighting of the damage types favors Electric because Electric is where your damage is coming from on [Serro]. Viral only needs to be applied enough times to get to its status cap, so you don't need a ton of it. Since Slash is our only IPS, you won't get any frivolous Impact or Puncture procs (Impact and Puncture will eat up a couple of damage instances to apply their status effects, so even though it's not a huge difference, using a weapon without them is strictly better).

In this setup, I use Aquablades subsumed over [Inaros]'s 1 to guarantee additional Slash damage and, more importantly, Bleed procs. Because of the proximity of targets in Sandstorm, electric procs are guaranteed to chain like crazy. Viral and Slash combo is self-explanatory. Regarding armor and shields, you can easily chain armor strips with [Inaros]'s 4, which will also spread like crazy inside the Sandstorm, relying on green shards to fully strip armor, though in most content, Bleed and Viral will just kill things anyway. Shields at higher levels might warrant changing your mod setup, though [Serro] is still up to the task; The innate Electric can be turned into Magnetic, which will let your Slash and Bleed strip off shields fairly easily. In this case, you might want to increase the weighting of Slash to stack Bleed more quickly. Remove [Virulent Scourge] and add [Buzz Kill] and [Jagged Edge].

The main benefit to modding [Serro] like this is that it costs almost nothing. No potato, no forma, and no expensive mods. Beyond all that, I do believe it to be effective, too.