Go for kage treasure first and hope you pull certain ninjas like mei, danzo, killer bee, gaara etc. You'll also be able to pull good commons to help out your team lineup. After 3 to 4 times you get a rare ninja, you might want to think about start pulling from the jin treasures to get roshi and han.

There's no trick behind the treasures. If you want a rare ninja, depending on the treasure, you need to hit a certain number of pulls to get a rare. Kage, Tendo, and Sage, treasures have a rare pull rate of 50-70 while edo and jin treasures have it at 30-50. It doesn't matter if you pull 10x once and it again later or do all 60 at once just as long you hit the range to pull. Also, only pull only when there is a seal rebate and it occurs every two weeks so its not that hard to be patient and you be rewarded with seal scrolls when you use them.

Someone already pointed out the bug but they haven't fixed it.

Why would you assume that? Look at what is common between the ninjas you can get in the treasure. The common factor is that these were quality ninjas back in 1.0 and logically putting a super rare in one treasure that was released in 3.0 into a treasure that was used in 1.0 doesn't make sense.