Although a buff on her W would be loved, Ahri is a rather well balanced champ right now.
It is VERY hard to farm as Ahri
Not true. I forget when in the game, but definitely early on her Q can clear the mage minions. If you poke down the front ones with your auto attack your Q can clear the whole wave. If you time it right you'll even poke the enemy laner.
As a champ focused on ability power your auto attack shouldn't have that much strength to it. I find early on I miss the last hit on enemy minions because I think it will do the mid game damage (what I'm accustom to) rather than the very little early game damage. Just gotta keep practicing last hitting.
Let your minions poke them down, use your AA when they're high to mid health, let your minions get them all the way down and then AA that last bit of health. If they're low and you try to AA twice, once to get them lower and once to finish it, your attack speed won't always be high enough to get that second AA in before one of your minions get the kill.
If you feel like using your abilities to hit minions leaves you open perhaps you need to evaluate why. If you're anywhere past the river, especially without wards, you are open. Buy a control ward on your first back and place it on the side that has the thicker wall. The one with the thin wall on your side of the river is good for regular wards because you can place them over the wall. This way you don't have to face check just to put a ward down. Anytime that control ward gets taken down buy a new one the next time you're at the shop. It makes such a difference.
Your Q gives you movement speed, so once you hit that wave of minions, run back towards your turret. There's not much you can do pre-level 6 other than poke them down, which is what your Q is for. If you find yourself needing health use your W to get your passive stacks up, and again go for the full wave. I usually get my E second, Q third, and W fourth. E second because that charm is great for interrupting anyone who gets too close.
I also like to get the refillable potion (150g) on my first back (I'll sell any unused health potions for it even)** because it refills** every time you visit the shop. That's that much more gold you can put towards other items rather than continuously buying health potions for their 50 gold. I also get Lost chapter ASAP (even before the control ward and potions, but don't forget about them) because that extra mana really makes a difference for your lane sustain.
After all that the only thing you really need to do is learn when to engage, and when/how to play it safe with Ahri. Take a look at some of her guides, and watch some streamers play through. She's a rather squishy champ. I'm a M7 main with her, but she was my first AP champ after being only ADC. It's a very different play style and takes some getting used to.
