I guess my main response would be to ask how you decide what the most important part of the skill is (and how you would arrive at that conclusion).
I could be wrong, but I get the impression that you’re basing this primarily on the name and description, both of which I’d consider to be small details in comparison to the main concept. They can very easily be changed without fundamentally altering the skill.
While it can, of course, work in both directions, for the majority of skills we’d start with the question of “What do we want this skill to do?” and explore that, with names typically being created later in the design process (and usually considered rather disposable).
I’m not sure if you’re aware, but Poison, in addition to being a stackable DoT, increases the Poison damage your character takes - and this effect stacks with each active Poison on your character. So my answer to your question is that Poison is fundamentally designed to grow exponentially more dangerous the more stacks of Poison your character has on them - and this, in my view, makes Aura of Decay more interesting than “you take Damage Over Time.”
Now, due to how the skill is designed, there’s a limit to how many Poison stacks it’ll apply - Poison has a fixed duration, and stacks are applied at a regular interval. After a very short period of time, it’ll get as bad as it gets… from Aura of Decay. But Poison is Poison - so when using AoD you need to be mindful of which enemies you’re facing, and what they are doing.
From a gameplay standpoint, this kind of skill dealing Necrotic damage to you and enemies makes it safer, easier to balance, and… honestly I think less interesting. It could be a good idea for a node on the specialization tree because it affords people the option of having a less dangerous self-damage component which is balanced against being less harmful to enemies - and this is all neatly packed in a “deal a cool damage type” package which doesn’t feel bad to pick up, which can be a concern for safer options which deal less damage to enemies.
There’s also a pragmatic side - would we prefer to edit a couple of text strings, or redesign the skill from scratch? We’re happy to take on more work where we deem it necessary, but if the issue is a name and description not being thematically on point… well, we can correct that by changing the name and description. If you’d prefer we tackle it differently, mind if I ask why? We’re not opposed to doing so, but I don’t currently see the need for it.
tl;dr: How do you decide the theme of a skill? (And why is your answer what it is?)
(This could be quite an interesting discussion! Let’s make it more prominent.)