Just to be clear 1st SR can be pulled between 900 and 1500 pulls. Most of the people i know got 1st SR on 1050. Guy from my Group is at 1400 + and still didnt get one. He made a ticket to check if its a bug or not and he got this answer

There is no exact drop rate of SR in GNW treasure, although according to players the drop rate of SR gets close from 900's can go up to 1500's, so no it is not right that you will obtain at 1050, can be before that or after that."

So you should wait for GNW rebate and try ur luck again. Dont go for 10 by 10 pulls now cos as i told you 1st SR can drop on 1500 if you are unlucky