Imagine you're from another country and have never seen any of these contestants dancing and today was the first time you saw each one dance. Pick any one performance of Isha (e.g. Zindagi ka Safar) and imagine watching only that one performance of hers. I'm almost 100% sure that you would feel she's brilliant and instantly give her a perfect 30.
What I'm trying to say is that the judges are supposed to rate INDIVIDUAL performances everytime. And each individual performance of Isha-Salman is PERFECT.
This is exactly the reason why the judges can't underscore Isha under the excuse of repeating acrobatic moves because the flawlessness of an INDIVIDUAL performance weighs higher than versatility.
Ofcourse, I personally don't feel she's that repetitive at all, but for those who do, it's just that she uses a bit of her acrobatics in every dance and that's all. It's her strength. Remember again, each INDIVIDUAL performance counts more than comparing the performance with past performances!