How difficult is it to survive in IIM Ahmedabad for a not so stellar profile student?

To answer this question you need to know what a stellar profile really is. It’s your particular skill set that makes you a good candidate for placements rather than just your academics and course. 

If you are referring to placements as survival then trust me there are jobs for every profile. You need to focus on two main things. Excel in your own field (Humanities or Commerce) and develop a good network. 

As far as the placements are concerned your particular background will fetch you the most suitable job.