Hey thanks for the post :) Yea I have tried a few times by rushing Hextech but I have actually found that Ahri really needs that extra bit of health and mana to stay in lane a little longer...Catalyst protector is a great way for any caster in my opinion to stay in lane that little bit longer....depending on how I do in the mid lane I usually buy a health crystal and maybe a tome....and upgrade them as I go.

Nice guide.
I use Hextech too, I get called Noob for buying it until everyone realizes its a handy tool for a very powerful combo, and to keep me in lane longer.
Though I actually rush my Hextech buy purchasing Hextech Revolver first, then work on my Rabadon's Deathcap for the ability power.
I have some pretty high kill-low death games playing Ahri.