1) Circle of Channelers: Pick up late mass of earth/stone. Drop on warrior/s.
Result: at least entombing the warriors for a length of time, potentially suffocating or crushing them. Probably will snap necks on impact if large/solid enough mass.

2) Channelers: create massive fire around warrior (Either with OP or by lighting the area on fire)
Result: suffocation of warrior as oxygen is consumed and, potentially, smoke fumes are produced

3) Channeler: Suck the air out of an area, creating a vacuum
Result: suffocation (do you sense a theme here? )

Just like any armor, there will be weak and/or unprotected points that could also be exploited by simple arrows, not to mention mind-guided arrows, swords and daggers of air. And, as a more insidious method, to one use spirit to sap the life from a warrior be flowing draining weaves between the armor joints? There woudl have to be room for movement, thus room for air and thus, feasibly, room for weaves. Oooo I wonder if you could just weave a fireball INSIDE the armor!! That'd be splendid!

Additionally, we don't know how the OP acts against c-dar in a non-aggressive manner. So some more potential possibilities. If you wrapped ropes of Air around a warrior in such armor, would the c-dar allow him to "break" the ropes? If you created a ground sink so that he sank up to his waist, would the c-dar allow him to just "swim" through the earth like it was water or quicksand?

There are any number of means that a channeler could, easily, neutralize and/or kill a warrior in c-dar. I'm not saying it wouldn't be a benefit, I just don't think it'd be a benefit worth the effort.