Only in an alternate reality is OST arty "really good".
-Air/off-map don't come until late late LATE game, cost a lot of munitions OST is starved of, require a spotting unit, are slow and easily avoided. Did you get that? I said EASILY avoided. These do not win games or even remotely make up for the vast disparity in effectiveness vs allied indirect fire options as a whole.
Don't make me cry, Just stop making blobs of shrecks, you will have those munitions supplies.
Just check the ladder ranking, Ost still win quite consistently.
Remember the meaning of asymmetric balance.( no pun intended.)
(Comments where based on 3vs3 or 4vs4 )