They are not weaker, maybe in terms of range and dmg . Mr. Someguy pretty much sums it up why they are so good . Fausts have an animation , which needs to be completed afaik.
So having a longer range to be fired at, higher penetration, and no seperate research cost is inferior? You're crazy. Also, faust animation is only 0.7 seconds longer than the AT nade animation, but surely thats too long of a time to wait.