Air is not the strongest element. It comes with its strengths and weakness, just like all the other elements.
Tenzin is fighting in a arena that compliments his elemental fighting style.
If he were on a boat it would be water fighting style that would be strongest,
If he were underground then earth would be a fighting style that would be strongest,
If he were in a enclosed space, then fire would be a fighting style that would be strongest.
Also tenzin has the home court advantage, of knowing the area very well, and also has experiance fighting a airbender(Aang)
It is clear that tenzin is the current most powerful airbender. That he is stronger than zaheer.
He could even take all the others in a 1v1, or even a 1v2. Perhaps he could even hold his own in a 1v3.
However he is not able to do this just because air is so strong. He is able to do this because of his own power and experiance. Otherwise zaheer could just negate him, and the addition of a second person in the fight would be to much.
Airbending is the most versatile bending other than fire bending, because it is a element you will always have available anywhere. Its fighting style can be effective in 1v1. Because the style is to dodge attacks, and strike when possible. While other bending usually has people blocking the attacks, or power through them, with dodges reserved for more dangerous attacks.
My only disagreement really was with you saying air is clearly the most powerful element. When to me it doesnt seem that way.
I am not sure if tenzin will be available for the final showdown. Im not sure whom korra will face.
But I think it is clear toph will show up at a pivotal time.
I am not sure about the red lotus lasting any longer than this season.
Nor am i sure if there will be a 4th book(though I hope so)
Any episodes with iroh in it are always good
This was a good episode though.
Final comment: That grandmas reverence of the earth queen is a bit creepy.
