By description it makes it harder for pets to hit. And elementals are supposed to ignore it.
But right now in sandstorm elementals get double penalty. They hit for less damage, because sandstorm acts like a shield instead which elementals ignore on self, but elemental pets themselves get hit in sandstorm for full amount. So your opponent takes less damage, while you take full damage if you are elemental.
If this wasn't directly addressed yet, no it is not "bugged" by definition of the word. Elementals ignore all weather effects. Sandstorm "reduces damage *taken* by pets," not "reduces damage *done* by pets," so elementals still take full damage. Elementals also don't lose accuracy in a Sandstorm, because the text "reduces the accuracy of pets by 10%", not "reduces the chance to be hit by 10%." It's all in the wording.