The bombing run in Ogri'la can be a real pain in the patooshka!
It finally ocured to me that I was approaching a 3D problem with two dimensional thinking.
This strategy works like a charm after a little practice.
The Set Up
1. After getting the quest, and before entering the bombing zone get some altitude and hit the "auto run" command; on my computer that is the Num-Lock key.
2. Set your flight trajectory to a 45 degree downward angle, and use the Straight-Up key to gain altitude at a 45 degree angle. This is the same key you use to jump, the default key is the spacebar.
This set up should allow you to strafe up, down, left and right with one hand. The other hand is using the mouse to control where and when you throw the bombs.
The key is to never stop moving forward.
Practice, practice, practice.
You will want to practice moving about in friendly territory first.
Once you have good control over your flight pattern go practice flying around in the bombing zone for a while. Don't worry about completing the quest at this point, just concentrate on avoiding the flack from the canons below you.
When you can fly through the bombing zone without getting knocked off your mount you are ready to add throwing bombs at the targets.
The Bombing Run
Here is my approach to the bombing run.
I think of each battery of guns and ammunition piles as an island. I fly to the center of the island at a 45 degree down angle. As I start the approach I will already have clicked on the package of bombs to activate the spell's AOE targeting.
As the canons shoot I will fly up and to the left or right for a count of 3 to avoid the flack and then return to my original course.
When I am close enough to the ground to see the green AOE target I throw a bomb at whichever pile of ammo is convenient. After I throw I leave the area by flying up and to the left or right.
Rinse and repeat. It only took a little practice to get to where I was able to do this quest in just a few minutes.