Don't think Bairstow should be dropped, he's played a couple of good knocks and if SRH removes him, then that's one less power hitter in a lineup where no one is particularly known for their hitting abilities. Pandey has been decent at 3 but he's been playing a tad too slow. With the form Williamson is in, he needs to bat 3. Pandey should be tried at 4/5 IMO. The best knocks that he's played for India in T20I's has been done in the 4/5/6 position. Playing Manish at 5 brings some cushioning to the middle order and might allow Garg to play in a more natural position nearer to the top of the order.
Samad should be backed ahead of Shankar, who's only there for the experience and to be a sixth bowler. Samad has shown a lot more promise than Shankar and needs more consistent game time to get him used to the IPL stage.