I agree. And the latest changes did exactly that - there DC now scales with there con score.. And there constitution scales with difficulty. I think Mr Cow had some hard data on this too somewhere.
And if he said:
I think your should adjust air elementals knockback DCs to X on normal difficulty, and leave elite as is.. I'd agree.
He didn't.
I'd like to see there knockback ability get a save - very high DC, say +5 compared to the knockdown portion, but also massive up there whirlwind damage to compensate (its currently around 2d6 dmg, even on high lvl elite versions)