SR of 90 is adequate when you're scoring 70 runs per innings like he is.The pace at which these runs are scored also matters. Rohit has been setting the stage. With Virat, he has slowed down throughout. While Iyer began slowly he has accelerated post settling down. Haven't seen that happen with Kohli.
Rohit had 54 RPI and Iyer had 48, because all 3 of them played different roles. Rohit the aggressor. Kohli to bat through the middle overs. Iyer the enforcer/rebuild job.