Another thought...
Should a Fireball Barrage Team enter the fray, have one Gnoll Druid or Marrash Cleric with the Air Domain as the default "Commander" of the air forces.
He flies at mid-height of the air defense, preferably under invisibility, possibly with a non-detection item. He's worth it, he's the ace in the hole. (Actually, I take it back, Gnoll Blight Druid on his Undead Giant Eagle Companion - always flies in the 700' to 900' altitude range to oversee the total air defense.)
If a fireball assault begins (and by all means let one or two impact - it's a really good plan, and there should be some bombardment success), have him climb to roughly the height where the fireballs originate from and:
Control Winds
Transmutation [Air]
Level: Air 5, Drd 5
Components: V, S
Casting Time: 1 standard action
Range: 40 ft./level
Area: 40 ft./level radius cylinder 40 ft. high
Duration: 10 min./level
Saving Throw: Fortitude negates
Spell Resistance: No
You alter wind force in the area surrounding you. You can make the wind blow in a certain direction or manner, increase its strength, or decrease its strength. The new wind direction and strength persist until the spell ends or until you choose to alter your handiwork, which requires concentration. You may create an “eye” of calm air up to 80 feet in diameter at the center of the area if you so desire, and you may choose to limit the area to any cylindrical area less than your full limit.
Wind Direction: You may choose one of four basic wind patterns to function over the spell’s area.
• A downdraft blows from the center outward in equal strength in all directions.
• An updraft blows from the outer edges in toward the center in equal strength from all directions, veering upward before impinging on the eye in the center.
• A rotation causes the winds to circle the center in clockwise or counterclockwise fashion.
• A blast simply causes the winds to blow in one direction across the entire area from one side to the other.
Wind Strength: For every three caster levels, you can increase or decrease wind strength by one level. Each round on your turn, a creature in the wind must make a Fortitude save or suffer the effect of being in the windy area.
Strong winds (21+ mph) make sailing difficult.
A severe wind (31+ mph) causes minor ship and building damage.
A windstorm (51+ mph) drives most flying creatures from the skies, uproots small trees, knocks down light wooden structures, tears off roofs, and endangers ships.
Hurricane force winds (75+ mph) destroy wooden buildings, sometimes uproot even large trees, and cause most ships to founder.
A tornado (175+ mph) destroys all nonfortified buildings and often uproots large trees.
Welcome the single most devastating environmental spell under 6th level. Even at 9th level caster and only Windstorm, flying PCs are in for a rude surprise as they lose almost all ability to control their flight. If the Air shamans have a tasliman that ups their caster level (even if only briefly 1/day) to get up to Hurricane or Tornado...well, someone's gonna have a bad day.
Oh, and since it's not technically an attack, just altering the environment, it shouldn't break invisibility.
How's them apples?
PS: Did I forget to mention that while the PCs are messed with in the Windstorm, the Shadows on air patrol rush in, and being incorporeal should remain unaffected by the winds, making them even more brutal.