This year we have been swept 3 times, and swept teams 3 times (in 3 game series). Compared to last season where the Cardinals were an impressive 7 & 1.
So how rare is a 4 game sweep? About half the teams have a 4 game sweep in any given season. Most only once in that time period.
I've included a link in case you are curious about non Cardinal specific data:
http://mlbsweeps.com/total-sweeps-by-year/Edited by implode at 09:01:15 on 07/21/16