What you say is true, Trans4M. =) But, personnaly, I keep a preference on Fox-Fire, because, believe me, even if Orb of Deception has true damage, Fox-Fire Hurts the most in the beginning, guaranteeing youto, when you hit all your E-W-Q combo, that minimum the half of your target's lifebar's gone. I think that this actually remains of the summoner preferences. Because both do a lot of damage if you use them correctly.

the thing with Charm is that Orb of Deception will be a guranteed hit if you land Charm. Just a matter of how quickly you can do it.

The combo I usually do is Charm > Orb of Deception > Fox-Fire. The reason is Charm will give me a clean shot at the enemy with Orb of Deception as the target will walk straight towards me and I only need to fire it straight towards them. Orb of Deception comes out first to ensure both hits will hit and then Fox-Fire will be guranteed to hit as it tracks champions who are too close.

For this very reason I would max Orb of Deception first like LostTRoll mentioned.

Well, you're right on some section. But for the skill sequence, I'll explain more clearly. I level up Fox-Fire first because it has a champion priority. So when you actually hit your Charm, you do this and it'll go on your target automatically. For the Q, you have to aim. If it misses, it's useless, so why should I level this up first ?It's a good harras, true, but still. I only use it to get my stacks up in the beginning, nothing else. Believe me,n in the beginning, Fox-Fire is the one that hurts the most.
For the items, you're not the only one that says that Rylai is good... Actually I never tried with it. It might be perfect with the slow and so. But... For the WotA... Actually imagine this, it can save your life more than once. You dived someone, then you get ganked and you have low HP. You use your last ulti to try to get away, then do you W, which will target the ganker. You'll regain some HP already, then you can try to hit your E and Q, to get him under your tower or something. WotA have been very usefull for me till now. For the Hourglass I understand what you say. Although, it can help. if you jump in the middle of the ennemies iwth ulti, for example, And you get targeted... Well activate it and the ennemies will be confused, then your team has two whole seconds to take them off. When you get out you use your last ulti if you can, if not well.... Try combo and GTFO. ^^ This is really for some more dmg and survibility. The armor + helps some. ^^ Well ofc if you're vs a full AP team, then you get something else.. BE SMART. Trolol. But it's true you can replace it with the Void staff. Although, like I said, it gives some less survibility. more dmg, but tho. You have already about 25-30% MPen with just runes and boots. Isn't that enough ? This is why I don't replace it with Merc Boots either. :D

Hope this cleared the things out for you. :3
And btw, I really think doran's ring is useless on her.. o.O I mean, it gives you HP, true, but you should rush the RoA first, and not waste your Gold on that.

i forgot 1 more thing; the build i use is:
dorans ringx2
boots
rylais(core)
sorc boots
rabadon(core)
lichbane(core)
abyssal scepter(core)
merc boots(core)
situational slot (may switch the order of merc boots with this)

rylais makes you laugh when top and mid switches and you play vs singed and others similer.

-hope this helps you devise a new and better build than ours

leveling foxfire first is bad during laning phase,since you most probably wont hit them with it. Now lets say its 1v1: orb of deception(Q) flat damage scales as well as foxfire(W); only half of the damage of Q gets affected becaue of mr, but all of the damage of foxfire will get affected by mr--i didint include the ap scaling because isnt affected by the order of sill sequence

i dont agree with clarity being good since it's only good for laning phase and pre-blue/ pre-rod of ages and ends up being a total waste.

spellvamp?? your passive already gives you 25%. to stack it up use fox-fire then when you do have 9stacks, poke your opponent and hit the minions at the same time. this saves mana and dosnt destroy thee camps too fast to get the 9stacks instead of using orb of deception. If theres anything you can replace it with, it's deathfiregrasp for that awesome passive and mana regeneration and cooldown reduction.

hourglass isnt as effective as you think. you dont have any abillity that works while youre invincible, for example:fiddlesticks ult, morganas ult, kennans ult, etc. You have charm that gives an annoyance to disabler(guys with alot of cc) initiaters, and carries.

so my recommendation is:
-replace WotA with DFG
-replace hourglass with voidstaff
-after getting voidstaff replace sorc boots with merc boots for that tenacity
-take clarity out of the viable section

--i dont play ahri much since she isn't really my playstyle. so my recommendation might be bad

p.s. dont jump into the middle.of their team O.O if you get cc'd their carries will obliterate you into oblivion--aka bad positioning-- you want get an angle behind your tank and charm dat ad carry then throw your skillset every 1sec, instead of being a nuker and blow it all up, for maximum potential of lichbane;theyll call you op if you know how to use lichbane. (lichbane can procs every 2sec)