Dear George
Congratulations on passing IPCC exams and joining articleship in Big 4!
Since your attempt is in May 2016, you can start with Accounts, Costing and Finance for sure. Since in these subjects, there would be no amendments. As far as other subjects like Law, ISCA and Audit are concerned, there might be minor changes (not for Law!!..since for you Companies bill would be applicable).
So,start these subjects may be after 8-10 months of your articleship, so atleast you would be clear as to what portion has changed and other things.
Now, for IDT and DT, there will be many changes for sure. Plus you will have to read case laws, amendments etc which carry significant weightage.
But, looking at the volume of the syllabus of Tax (both DT and IDT), yu should at least start with some topics so that in the end you don;t find it tough and lengthy.
PS : I am an article in Big 4 too, so suggesting you accordingly. You may get many opinions on this but the key is to do regular studies!
Regards