Darr, who was hitting just .215 coming into the game, had four of Arkansas' 10 hits, including his fourth homer of the year.
Arkansas (39-22) returns to the CWS in Omaha, Neb. for the first time since 2004 when it also beat Florida State.
The Seminoles (45-18) had taken an 8-7 lead in the top of the ninth when Stephen Cardullo singled in two runs and then scored a short-lived go-ahead run on a Jason Stidham single.
Arkansas' Stephen Richards (6-1) got the win despite giving up three runs in the ninth. Jack Posey (0-1) took the loss.
North Carolina 10, East Carolina 1
CHAPEL HILL, N.C. Alex White struck out a career-high 12 batters while getting plenty of help at the plate as North Carolina beat East Carolina to open their NCAA super regional series today.
Kyle Seager had four hits and a home run for the Tar Heels (46-16), the No. 4 national seed. North Carolina went ahead with a pair of runs in the third inning, then blew the game open with seven more in the sixth. The Tar Heels can clinch their fourth straight trip to the College World Series by beating the Pirates again Sunday.
Brandon Henderson hit a solo home run in the second for the Pirates (46-19), who didnt get much else against White. Seth Maness took the loss, allowing 13 hits and six earned runs in five innings.
Virginia 4, Mississippi 3
In Oxford, Miss., Robert Morey pitched four hitless innings after giving up two runs on his first three pitches and Virginia took advantage of an eighth-inning error to keep its bid for the College World Series alive.
An errant throw by second baseman Evan Button helped Virginia (47-13-1) to a two-run eighth inning when Franco Valdes drove in one run and John Barr beat out a double-play attempt to put the Cavaliers ahead.
The defensive difficulties wiped out a nearly perfect outing by starter Drew Pomeranz, who struck out 10 despite a blistered finger in his bid for his third postseason win but finished with a no decision for the Rebels (44-19).
Barr had two RBI for the Cavaliers.