I decided to play intensively Para during a month, i went down from top200 to top700 in 1sv1 and 2vs2, now I gaining rank again since I don't use it anymore
Para and pathfinders are too expensive and too squishy and they do not have smoke nades.
No smoke = in trouble vs a defensive Ostheer
Too expensive = Heavy MP bleed vs OKW with 1 or 2 LEIG or vs Luch
This + the nerf of the bombing run.
The doctrine is funny and I think a lot of people like it, but it is definitively not meta in this current state of the game.
You have 3 basic doctrines (including Para).
Armor is basically really good if you decide to go T1 and T2, the M30 you get CP9 is a really good Tank Destroyer (zero dps vs infantry) for your late game.
Infantry company is good if you plan to go T2 first (captain), M1919 on your rifles make them beasty, you can build sandbags wall and plant mines, you can call a mortar if you want, you have a useful off-map arty and if you really need it a Priest to arty your enemy position. I do not recommend you to build the mortar or the priest every game, see if you really need them.
Next you have 5 other commanders you may drop as warspoil or buy it as DLC. To make it short if you decide to buy some: Perhsing commander and Calliope commander are the best one. The other 3 are far less interesting and require you to gain some skill in the game and gameplay to correctly use them and gain benefice from.