I don't think any of this is gamebreaking, but this is what I was thinking since I see fewer variety of ranged carries in games...
Vayne: +5 base movespeed
-All her movement nerfs have really affected how she plays. With the most recent PD nerf she is slower lategame as well. Some other carries have more than 300 base movespeed, so this will make her a bit more on-par.
Miss Fortune: 5% more slow on make-it-rain, ult changed to magic damage
-The ult change to physical damage actually reduced the damage of the ult on targets like carries, since everyone gains armor every level, and not everyone gains magic resist. The 5% slow is to make the slow on-par with Varus.
Varus: 10/15/20/25/30 magic damage on blighted quiver (+1 damage per level basically)
-Because I hate the odd number 26... Plus I think this dude is outshined by a few carries, this small buff might help him.
Tristana: 70-75 mana cost on Rocket Jump
-Mana cost is too high on this move. Tristana has a very small mana reserve. Either buff the mana reserve or reduce the cost a bit.
Caitlyn: Snap Trap binds for 1/1.25/1.5/1.75/2 Seconds
-Atm it is pointless to level Snap Trap unless you want it to cooldown quickly. Leveling up the net gives you added slow every level. Doing this will give players a choice and will make the traps better lategame when most ppl have tenacity.
I think most of the others are fine and see alot of play... Except Sivir... She's just a wreck after the rework imo... So, I'm not even going to get started on that.