Does anyone else feel that Sivir is weak?

So, Sivir

Whenever I play Sivir, she never feels particularly strong. I mean, yeah, it is fun sending out her Q and watching the enemy health bar go down, but other than that, she doesn't FEEL strong. Her ultimate disappointing, and the fact that she only has two damaging abilities (one of them is just a faster auto attack that does less damage) just makes her seem less like a carry and more like someone who chips helps teamfights with pretty decent AOE damage and boosts people's speed. It is definitely nice that her E blocks a spell (if you time it right) but the mana regen is negligible late game, and her kit just feels like it needs something more. Her laning phase is pretty good if it weren't for the fact that she always seems to be out of mana, but mid to late game, she seems to fall behind. Maybe it is just me, but I feel like she could use a boost to her kit. Maybe add some AS or AD on her ult, or make her Q crit. Maybe someone who really knows Sivir could shed some light on her situation for me, because right now, I can't see any reason to use her over someone like Lucian, Vayne, Kog'maw, or almost any other ADC (barring ).