teamplay only really kicks in at top 30 play.
Imo it depends on how u define the term teamplay. If teamplay for u is you and your teamm8 being present all around the map (the VonSildur/HooliMan god mode style) it would kick in only top 30. But i think teamplay is already there if you got your tank at the right moment there to help your teamm8 out, or you got your units on the spot where the enemy is about to flank. Or when u do a single combined push on one of your opponents.
For example i played with a friend of mine against wuff and some other guy yesterday, me and my friend were both struggling until i shifted to the side of my friend as well (and forgo our fuel point) to help him destroy a sovjet stronghold. we completely demolished my friends opponent (together), which allowed us to get back in to the game. These kinda actions were you play together qualify as teamplay too imo.
so since i am not top 30 i disagree with the statement that teamplay only kicks in the crême de la crême of the ladder. My point is that teamplay is important and also can be a crucial factor on lower levels. (it might not be the godmode teamplay of the guys i named ealier but it is still teamplay and will win u games if u work together on the right moment)
TEAMPLAY MATTERS!