I can understand the idea that air elementals knockdown their foes, and in principle I am ok with this.
However, when a character with Epic gear can be knocked down from long range by a CR 14 Air Elemental, then swarmed by a group of more CR 14 Air Elementals and be chain knocked down (making it absolutely impossible to do anything)...that's not fun.
I propose that Air Elementals lose their ability to knockdown characters at range (they can already use Gust of Wind for the slow effect then catch players anyway), and that in melee range their constant knockdown attacks be replaced with an AoE knockdown attack with at least a 10 second timer. As well as losing their knockback effect as well. Wiki source
Players, especially capped characters with Epic gear, should not have more trouble with Air Elemental trash-mobs from Gianthold than they do with with named monsters from Shavarath or Epic quests.