I am deeply involved with the placement process at IIT K and I would like to shed some light on the placements here that I have seen myself.
Placements depend on a lot of factors. One of the most important ones being a good job market, with firms willing to hire graduates right out of college. Secondly, it depends on how good the students of a particular institute are, which is never a problem for at least the top few IITs.
Now comes the question of M.Tech v/s B.Tech v/s Dual Degree, and whether M.Techs are hired by companies or not. Usually, masters students come to IITs by clearing GATE, which is not considered as tough as JEE (and I partially agree with this). This answer can be split into two parts :
1) Non-core profiles : Companies which come for analyst profiles, like financial firms, stock trading firms, investment banks, etc have the notion that if a student has not cleared the JEE, he/she is just not good enough for their profile. That is believe is false. If you look at the recent past, companies have slowly, but surely started opening for M.Tech students for recruitment as well. Although the level of recruitment for Mtechs in this area is still really low.