[Lazy_Perfectionist]

Wait. You're talking about missile resistance bless as needing help? First off...
Lesser Air Bless shouldn't be compared to the Greater Astral bless.
Lesser Air VS. Lesser Astral
Helps versus ranged fire/No help against ranged fire.
No Help versus Shadow Bolt/Helps against Shadow Bolt and other MR spells such as Decay.
Helps versus some fire and many earth spells/No use against spells that do not check MR.
Becomes moot when Arrow Fend is castable/Stacks with other MR boosters.
Air spells not always castable/Astral spells not always castable.

Regarding its value for Air Nations, I've got no opinion. But it has been invaluable for certain games I've been playing as nations such as Atlantis that have no missile troops. If my current build supports an inexpensive air bless, I will take it.

My current pretender build for BAG involves an imprisoned Titan with Air 6, Earth 9 for a bless. The bless is not factored into my long term strategy, but has, in test games, allowed me to take 20 provinces by the end of the first year. A lot more than I ever expected a nation like Late Era Atlantis to manage. Of course, in MP, I'll be running up against human controlled nations as well. And as my Arssartut are capital only it won't be useful once I run out of independents to massacre. Fortunately, I've got other plans for that stage.