I am really interested in getting the T2 endoskull set but haven't been able to find a disc by disc breakdown of exactly what's in the set. Could someone here who has the set or can find the information tell me, disc by disc, what's in the set ?

Well, four of the discs are the T2 Extreme 2-Disc and the T2 Ultimate 2-Disc sets, and one disc is a digital copy. I think the other two are a 2-disc Blu-Ray? With the Extreme and Ultimate sets, there is literally no difference from the ones already on the market, the same discs are included with the same disc art and everything.

There are 6 discs total.
The Blu-Ray Skynet edition is only 1 disc, the Extreme and Ultimate versions are 2 discs each (the previous regular DVDs as driodguy stated), and the last disc is the digital copy.

Cool. Thanks.