Yes, the headline says it all. It's hard to win games when you score three runs or less: since 1901, all teams have a .228 WPCT in such games.
Right now, the St. Louis Cardinals are winning at nearly double the frequency of the average team in such situations: as of today, they are 19-25 (.432) in such games.
That ranks 16th all-time at the moment--though, of course, it's subject to change over the second half of the 2015 campaign.
As you might suspect, it's a distinguished group of teams. 36 of the other 45 team-seasons on the list (80%) went to the post-season, and twenty of them wound up winning the World Series.
With the recent emphasis on offense, it's been awhile since any team has made it onto this list--the last time was in 1995, when the Atlanta Braves did it.
In fact, 26 of the 45 occurrences took place during the Deadball Era. Six of them came into existence via the performance of the Chicago Cubs, whose pitching was so dominant in the years 1906-10 that these six .400+ WPCTs in games where they scored three or less all rank in the top fifteen all-time.
It appears that there are only four cases where teams with .400+ WPCT in such games faced off in the World Series (1909, 1911, 1951 and 1954).
Teams that play a lot of these type of games don't tend to be a lock to win the World Series, however. Teams who played 80 or more such games over the course of the season include six teams that didn't make the post-season at all.
There's an interesting difference between two adjacent Cardinals teams in the 1960s. The 1967 squad had 63 games in which they scored three runs or less, a .444 WPCT in those games (#5 overall) and won the World Series...while the 1968 team had 94 such games, a .436 WPCT in those games (#13 overall) but came up short in that year's Fall Classic.
This year's Cardinal squad is on pace to wind up with 81 games where they score three runs or less. That's only 11th overall in MLB this year, so they are not setting an alarming pace in this statistical subset. But they are chasing the 1968 Cards in terms of percentage of overall wins when scoring three runs or less: they are currently at 34% (19 of 56), while the '68 squad had 42% of their wins in such fashion (41 of 97). That's the highest percentage of low-run scoring wins, just a tad more than the 1918 Washington Senators (30 of 72, or 41.7%).