Ignite is "risk for kill" summoner spell, great in overal, but teleport is more "strategic" summoner spell to win game. If you get used to play with Ignite, its all right.
Exhaust is "face to face" summoner spell, you have to be enough close to your target to cast it and other reasons are:
You already have slow {W}, disable {R} and protection {E}, and you can cast them very often. Ignite is always better for her than Exhaust. And if you are chasing an enemy, do W for speed yourself and Q+W (E+W) to slow target. This is why I didnt mention Ghost and so.

Hmm I really like how you named each skill combo thing. You seem to really understand orianna and items and the such therefore Im going to ask teleport? With a burst mage like her it would seem ignite or exhaust would be a better choice? You mention ignite but not exhaust. Just because your not the tank dosent mean its not a viable option. First blood, that 2 seconds where your opponent is doing almost no damage to you can catch them offguard and allow you finish them off then you can port back and walk into lane without even losing exp to your opponent. Just thought I should mention it. Anyway otherwise really great job, look forward to future guides.