I have gone through the faculty profile given on the official website of IIT Mandi. It looks similar to that of all newly established IITs, except for IIT Gn and IIT H, which are better than the others.
One of my friends is also a student of the Mechanical branch at IIT Mandi. Most of the faculty members in the Mechanical branch are married couples. One of them got a job here and after that, they recommended their spouses.
In terms of research, the branch is not that good. Most of the faculties just mug up a research paper and publish a new one. One of the faculties became associate by doing the same. If you want to pursue higher studies in Mechanical, then don’t choose IIT Mandi.