Well, I went to IITM for civil (which was NOT the least attractive field in 1985-90 but was after electronics, electrical, mechanical). I had the second highest JEE score in civil and was one of the few who could have got into a "higher ranked" area, but joined civil eng out of interest (heck, my dad is a civil engineer, and so is the only sister I have too
) ... The lowest ranks in IITM those days were around 1200, and civil started at around 650 and closed around 1000. Only 240 students were admitted in 1980 in 8 fields.
I do remember a few bad professors but who stays in mind are the great professors I had in most of the important subjects (but only about 5 or 6 such profs though). I still teach some of the things I learned from those professors, pretty much how I heard from them. The students never felt that any of them were more intelligent, but we did respect a few of them for their knowledge of the field, passion and the way of teaching.
There was only one professor in civil then who was an earlier IIT BTech grad, but they hired quite a few of such faculty from 1990 onwards. I had written to all the IITs after I got a tenure-track faculty position at Univ. of California, saying I was ready to drop it and go to India. Only 3 directors replied and none could offer me a quick interview and position. Everybody in India (including a couple of professors at IITM) asked me to not take a risk and just to take up the position in the US, and here I am still, after 23 years. But every time I went back to IITM, I felt that the faculty quality was improving. But I also feel that the hiring process is still quite poor, in identifying and selecting topnotch PhD grads from abroad as faculty. I have seen some poor hires from the US while I am aware of brilliant ones who would have gone to IITs but weren't considered, because the decision-makers in IIT are often not up-to-date on US faculty who are producing good PhD grads at any time, and got fooled by some people too.
But I have no idea about how the JEE process or the exam is these days, which was the starting question.....