Idea for splitting marksman into two subclasses
http://na.leagueoflegends.com/en/news/game-updates/gameplay/dev-blog-classes-subclasses Here's the post for context for those who haven't seen it
Every other class in the game is going to have two distinct subclasses, and they say marksman are too similar to split up.
My first thought was that Marksman generally fall into two categories, I would call them "Rangers" and "Hunters"
"Rangers" are people like Ashe, Kog'Maw, Caitlyn, and Jhin, who excel by staying at long range and can unload a lot of damage from there. They tend to do best when a team protects and supports them, and can often unload obscene amounts of damage in the right position, frequently to multiple targets. They usually use extra range on autos or powerful long range spells.

"Hunters" are people like Vayne, Lucian, and Kindred, who can fight their opponents more aggressively. While they still need a team to protect them, they can often do more on their own, some of them even being powerful duelists. They do best when a team can set up their damage and chase potential while still having enough peel to keep them alive. They usually rely on mobility or debuffs to stay alive and have less raw damage potential than Rangers.

I don't know what I'd call
and to be honest hes pretty unique.
Obviously there's a few places that it's not a perfect definition (Ezreal is very close to between). Overall, however, these two things seem to be the general designs behind most marksman - either they sit in a safe position behind tanks and unload anus-destroying damage, or they're slippery and persistent combatants and always threaten to turn or clean up a fight if left unchecked. I will say there's a decent bit more Rangers right now, but a couple of them could be argued as a Hunter and it still seems like a clear duality among the marksmans.
TL;DR split marksmans into range and utility vs mobility and dueling.
Feel free to say whatever you think.