User blog comment:Willbachbakal/Classes & Subclasses My Way/@comment-1920550-20160605210254/@comment-1330314-20160605221351

I think Vayne is currently both a Skirmisher and an Eradicator. She has the general dueling power of a Skirmisher, as well as some level of target specificity with her W, but also the persistent damage and general lack of downtimes of an Eradicator. I wouldn't exactly call her a hybrid, because like several other marksmen she has the strengths of both subclasses without making a real tradeoff besides a weak early game.

As for Caitlyn, I think she's a Skirmisher because she's built to snipe single targets and duel with them to some extent with her E and Q, with downtimes mainly dependent on her spell cooldowns. Her damage is also relatively target-specific (i.e. she can only Headshot enemies marked by her spells or by consuming her passive, and she usually focuses one target), and lacks the significant AoE or powerful steroids that often define Eradicator-type marksmen. She does have some Artillery/Bombard flavor due to her range, but unlike most Artillery champions she doesn't actually have very good back line access (her Q, E and R are all mitigated or blocked by front liners), which is why I wouldn't call her a hybrid of that subclass. She also does have some crowd control, but I don't think it's really Commander-worthy, particularly since Commanders use their CC/utility in the service of their team whereas Cait's CC is mostly pretty selfish.