HR to I/O?

Hello Everybody! I have been struggling with the decision to go back to grad school. I have been working in Human Resources for the past two years after completing a Bachelors in Psychology/Music and a Masters degree in HR. When I was considering my first go around with grad school, I was debating between graduate programs in I/O Psychology and Masters programs in HR. I ultimately decided to go to business school and get a Masters in HR since my undergrad was in Psychology and I thought having degrees in the Liberal Arts as well as Business would make me a more "well-rounded" candidate for jobs. However, now that I have been in the working world for a couple of years now, I am wondering if I should go back for a degree in I/O Psychology. My areas of interest include Talent Assessment/Selection and Talent Management. I have found that my Masters degree in HR, while certainly very closely related to I/O Psychology, did not give me a lot of scientific rigor when it comes to approaching topics such as Talent Assessment. I am currently in a position where I do Best Practice Research and Data Analysis for our Diversity & Inclusion department. My boss has a purely HR background, so she is not very helpful when it comes to developing me from a statistical or research background. I also realize that going back to grad school would be a significant time and financial commitment--I would be going back to develop skills that I feel are crucial to be successful in my areas of interest--but could I gain those same skills from 5+ more years of work experience? That way I would not be sacrificing my salary, and continue to gain valuable work experience. Would the value of a PhD outweigh the cut in pay for 5 or more years? Could I gain enough experience in the working world that a PhD wouldn't add any additional value? I'm curious to hear your thoughts! Thanks so much for your perspective!