How are papers set by IIT Delhi for the JEE Advanced?

IIT Delhi has set papers twice in 2012 and 2013. However, there is no fixed level of difficulty for this exam as the final paper is not set by a single IIT. Rather, it is assembled after the inputs of eminent professors and experts of all IITs.

• First, a mixed team of professors from different IITs is formed by the concerned IIT
• The entire team is made to stay in one place in individual rooms. 
• Professors will be given time and material to formulate questions
• Whenever they have formulated one or more questions, they will go to a highly secure room and write down the question
• This process is repeated till multiple sets of Physics Chemistry and Maths are ready.
• These sets are then submitted to the team leader who vocoders the final set of paper

This is how a JEE paper is set and thus predicting the level of difficulty is almost impossible since it’s the work of multiple experts.