Thanks everyone for the agreements and disagreements alike. 
A lot of good points have come up here. I want to do some more tests later today to get her reload speed and also to measure, as best I can, her melee hitbox.
Some observations I want to touch on first:
This is a solid observation, but there are several precedents for secondary attacks doing more damage than primary attacks.
-
Ambra’s secondary, her Scorching Strikes, does more DPS than her beam (contingent on Heat.)
-
Reyna’s secondary, her plasma pulse, does more DPS against shields than her primary.
-
I believe Shayne’s ranged secondary does more DPS than her primary only if she uses the boomerang bounce helix (and can be further improved with a boomerang damage helix.) This is especially true when Shayne is missing Aurox, which lowers her primary DPS but not her boomerang DPS.
-
El Dragon’s clap hits multiple targets with his l3 helix, so in theory would deal more DPS when he is targeting more than one enemy.
What’s striking about these examples is that so much of it is contingent. Reyna’s plasma is usually weaker than her pistol, but not against shields. Ambra’s secondary scales with her character resource. Shayne has to take certain helix choices, avoid others, and be without Aurox for her secondary to really outstrip her primary. And Dragon needs to clap multiple targets or else his primary DPS is far higher.
My suggestion is that Mellka (and perhaps Caldarius) could also enjoy contingent competitive secondary melee damage. This wouldn’t make them primary-melee characters any more than Shayne is primary-ranged because she can potentially kit herself out to be a boomerang monster.
What I think is the case right now is that Mellka and Caldarius are meant to have symmetry with melee characters who have ranged alt fires. For example:
Deande - her thrown fans do 61% the damage of her melee fans
Shayne - her boomerangs (without the bounce) do 69% the damage of her melee hits w/ Aurox
Pendles - his throwing stars do 36% the damage of his melee
The problem is, these lower damage outputs makes sense because the alternative is no damage. If Deande can’t reach an enemy with her war fans, then her ranged is the best option she has. But if Mellka can reach an enemy with her melee, she can also reach them with her ranged. So while these appear to be symmetrical design decisions, in practice, they leave Mellka (and Caldarius) with an attack option that is never clearly superior - in the way that thrown fans are clearly superior to not attacking at all.
I’m going to test her melee hitbox today because I suspect it’s not nearly as forgiving as the melee hitboxes of other characters, including Caldarius. But on the subject of accuracy:
When Mellka misses ranged shots, the damage drop is less serious than if she misses a hit from her melee chain, in which each hit counts for more. Consequently I am not certain that the accuracy argument is quite so cut-and-dry. Mellka has poor melee range and lacks a stun to keep a character stationary long enough to reliably crit them; if a character moves out of Mellka’s effective melee range, she will miss regardless of how accurate she is, whereas if she is firing her primary, this isn’t an issue.
Now, caveat: I’m almost always stuck on a red bar connection. Melee is miserable for me on Mellka because the server conspires to ensure that a moving character, even slowed, is always just out of reach of my hitbox. I don’t have nearly as many problems with Galilea, whose hitbox is incredibly generous and whose spin is always reliable.
If you are right on top of a Montana, Attikus, Kleese, or Toby, you may as well open fire - you’ll hit them. If a Thorn is darting around you, you’re likely to miss many shots from your primary, but given the fact she’s not only moving laterally but also away from you, you are equally likely to miss a hit or two from your melee combo, which is a proportionally greater decrease to your DPS.
I agree completely with your analysis and suggestion. Her venom really is the nail in the coffin for her melee potential. There is no way to apply venom via melee secondary (unless we count Spike, but that’s on cooldown); there are two ways to apply it using her ranged primary. Therefore, to effectively melee, you have to first initiate with ranged anyway - so why simply stay at range, where it’s safer and both your damage and accuracy are better?
I’ll post more later when I do some more tests!