I'm going to focus on Cassiopeia's Twin Fangs(E)
http://fc06.deviantart.net/fs42/i/2009/107/1/1/Snake_Muscle_by_ripped_saurian.jpg
The focus on her E and the funneling of pretty much all of her power into an up close point and click spell that does literally nothing but damage...may in fact violate the very concept of a poison mage. Typically the archetype is supposed to land their poison (s), and either they a) GTFO if it's 100% damage based or b) if the poison is debilitating, proceed to build up the poison until the enemy is so weak they pose zero threat
Regardless of the style of poisoner that they are, the weakness should always be a direct upfront confrontation. Either the enemy jumps into her face and pounds her down before she can scurry off, or the enemy jumps into her face and pounds her down before she can further debilitate them to the point of helplessness.
Her Twin Fang ability shits on that very weakness. And as you remove such a role-identifying weakness of a concept, you in turn must break away from the concept in order to find balance.
Theoretically speaking, her Twin Fangs E could have served a purpose as a defensive last resort effort to defend herself if the enemy gets too close to her (you know...like snakes in real life). But that is the best case scenario for her to stay consistent with her archetype, as when you make her E a 100% damage point and click ability, there's not much you can do with it is there? That is where making her E consisting of 99% of her kit falls apart.
Now as for the purpose of that picture. That's what a Twin Fangs (E) Cassiopeia is reflecting.
And if she isn't a poison mage...then why the hell do you base her off a snake and gave her an appearance and personality that screams poison using harlot?
If she isn't a poison mage, what was she supposed to be? What about her appearance exactly screams marksmen?