Luftwaffe Tactics is generally the most useless doctrine you can go with PE.
Just where did you hear that? It's not true at all.
Luftwaffe is one of the most powerful doctrine in the game for sure, especially early and mid game with its usefull and strong units call in. It can be good late game too with Flak 88 (situational) or Henschel 129 (which makes enemy armor become nearly useless)
A Fall squad hidden in cover in some far away points can wipe out whole enemy squad if your opponent fail to notice even a second.
Butterfly bombs can be used to reduce enemy sniper's effectiveness too.