ele damge

out of air, earth, fire, and water which type does the most possible damage?

Most possible damage has got be fire because of aoe.
Most possible damage on a single target has got to be air.

What armor value?

Yeah armor value needs to be known here. Id say single target, full energy, Mind shock is pretty high. Aftershock is too on a KD. Before AOE update, meteor shower owned it all. Now, Id still say fire can put out the best damage overall, but 1 single blow,... Id go air.

whats the best kind of armor ?

There's no firm conclusion.

Looks aside, it depends on what kind of elemental damage you'll see the most of. Traditionally, that's been a close call between fire and water/cold. But the two new character classes in Factions do earth and lightning damage, so I imagine that will even up a lot now.

It depends upon what you want to do. Search the forums, this has been covered a million times.