Where can I find raw data for DCI sanctioned Constructed tournaments?
In terms of offline (non-MTGO) information, the only data point that is brought away from a tournament match is the match record - mulligans, die-roll winners, and life totals are not processed in any way.

There are not any resources online with general match records (i.e. how often matches end 2-0, etc.) that I am aware of. You can go into the archives of GPs and parse the information from the round results pages if you wanted to, but that's likely about it. I'm confident WotC has the capability to derive this type of information internally, but the data for more global audiences to derive it is not public. (nor would WotC likely make such data public)

The site you linked gets it's information by monitoring Magic Online and recording metadata based on games played there - there's definitely more data there, but you'd need to keep in mind that MTGO and paper Magic may have different results for different events, especially when you take into account the difference in draw procedures, and the occasional prevalence of decks in paper Magic which cannot be effectively piloted on MTGO. (or vice versa)