I don't want to get into the statistics and the technicalities of the new buff, but I played a match earlier today where the enemy team secured 3 barons in a row (with us securing the last one, late-game) and we still beat them in team fights. Mind you, we were also behind in objectives and team gold.
http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1637771224/47583609?tab=overview
They had an advantage over us all game and we beat them in some important team fights (or they would get caught out).
The game did last for 58 minutes though. It was a grueling match, but we pulled out ahead because we would either wait until baron wore off, or find good openings in team fights and take advantage of it.