Has anyone calculated out standard devs and such?
In lieu of detailed stats on bet sizes and such, I can tell you that the site was about 1800BTC up when turnover was at 180KBTC, about a week ago. I think until that point almost all of the betting was from small fish.
Since then several whales have been betting big and doing well.
You might be interested to see the results of this simulation that I ran a few days ago. It basically takes as a starting point that there is a whale with a bankroll comparable to the house's bankroll, and the whale bets the maximum until one side or the other goes broke (i.e., the most extreme and aggressive whale scenario theoretically possible).
https://bitcointalksearch.org/topic/m.2762706
https://bitcointalksearch.org/topic/m.2765772
It is not uncommon for the house to go way, way down to such a whale (like 80% or more). So the house being 5,500BTC down vs expectation isn't particularly shocking, if most of the turnover was coming from max bets, or close to max bets (without seeing the stats no-one can say if this is true or not). The good news is the house always wins in the end.