Well, i think that the paratrooper are still useful, they're vulnerable during the descent and to anykind of armor attack, but they can act as light infantry, doing hit and run, they don't have any heavy equipement, so they main job is dirupt and confuse the ennemy command chain, for exemple, you are defending a combat zone,the ennemy just drop some paras behind and on you, there's some ennemy heavy unit preparing to attack from the front, what will you do ?? Send the armor to crush the para and let the infantry defend against the heavy unit or attack with infantry and defend with your armor ?? If u send infantry to fight, there's a chance your infantry will be deafeated or sustained heavy losses, but if u send ur tank, what will u do if the ennemy units pierces ur main defence line ??? Your armors are fighting against para, u cannot just take them out of the fight like this, so it's confusing the ennemy and opening a second "front". Or you can always drop them far back to cut the supply line like bridges and main road or even, take the ennemy airport !