DADA is just not picked because, Dhoni does not want him in the team.
If u take performance as a base, Ganguly should be in the team. He is scoring runs consistently and has been MoM many times recently ( including Tests against South Africa)
Even in IPL, he gave a good alround display. He took 7 wickets at very good economy rate and producted some match winning knocks.
If performance is the basis, then DADA should be in the team.