I'm going to play a part devil's advocate as well as a bit of true feelings here. I'm not a fan of this sort of discussion because all champions are balanced when you simply lay out a counter to every spell.
You can dodge Q, but it's projectile speed makes it difficult to. At max range, sure, but in lane, it's designed as a spell to be able to land most of the time, or else it would be buffed to compensate. The speed allows her to reposition as you dodge to align the rest of her spells whether Q hits or not. Even if it's not a 100-0, it's devastating with only a marginal mana cost to her.
Her W is an all or nothing spell, but it's not a core farming spell. This means that in theory, she should only be hitting W when she's attacking you. If she is hitting W, it's assumed you are in range of it so therefore, you will be hit by it barring extraneous mobility. Flash is not an argument for counterplay for this; the cooldowns don't even remotely align. So there is no staying out of its range because it's only activated when you're in range. If you're in range, it's most likely due to charm, her ult or your own engagement. It's not like Q that you can simply bait, not against any reasonable Ahri anyways.
E, yes. Stand behind minions. However, this nearly guarantees taking a Q. It also has incredible synergy with the rest of her kit, namely the ult. Her ult nullifies the creeps. It's also a great anti-gank tool. Her ult is the ace up her sleeve, but her charm-Q combo gets her out of most situations partly due to CC, partly due to mobility. Ever since losing damage amp, though, charm has been a simple spell and I've got no gripes with a linear, slowish CC.
Ult. This is why Ahri is hated. Everyone has fought linear damage, CC, passive damaging spells (W). But her ult is what makes her such an amazing pick. During her ult, she becomes the single most mobile champion in the game. Even a 45% cdr, max mana kassadin at level 16 can't match her mobility in this state. It's what makes her so versatile and a jack of all trades mid. It's one of the ultimate defensive CDs, one of the ultimate roaming CDs, one of the ultimate pursuit CDs, one of the ultimate damaging CDs as well. The way it's set up is also in a way that doesn't force you to pick one of these options. On a three charge system, you can mix and match various strengths for what seems to be one of the best spells in the game. It can be a defensive cooldown transitioning into a pursuit cooldown, into another defensive and many other combos. I know it sounds like I'm overplaying the ult, but it really is what it is. She's one of those carry champions that has her power backloaded into her ult. The W is decent, situational. Q is good but predictable and decently avoidable. Charm is the same as Q but a little easier to not be hit. But the ult is just a cooldown. There's nearly no counterplay to it when it's off cooldown. You can't zhonyas it, can't stop her from using it aside from CC, the counter to every single champion in league of legends, can't reasonably get away or chase her, etc. When she uses the ult, she becomes just a bit too versatile.
In lane, her ult also nullifies her weaknesses. Her ult prevents minions from being a factor for charm, her ult prevents you from staying out of range of W and her ult prevents you from simply dodging Q. Even if gated by CD, it simply nullifies all the counterplay listed above in your post which isn't often seen in champions.
150 second CD is the only reason she isn't spammed endlessly in games. Early game it's a bit of a cooldown. But the impact that ult single-handedly can make is what pisses people off. She's not OP, to me, in the sense that she hurts the game. She's OP to me in that she almost cannot be a bad pick. Even a marginally competent Ahri player can confidently pick her into most match ups and most comps and do well.
"Why you hate me summoner?"
"MUAHAHAHAH!"
out*[slayer-jinx-unamused]* )