because so many non-finance (above 80%) guys are applying for this.
Kachidoki, you might be overqualified, if you know some naive profiles. do not believe the reasons of rejections that they told you, it is just like good man card.
I am not sure whether experience in IB would help you a lot in terms of application, but that experience would definitely be helpful down the road when you start your finance PhD study. It will give you better intuition when trying to find explanations for your findings.