Based on my computer rankings (of best teams, not most deserving of tournament bids), here is a similar breakdown...
Top left (Whitman) bracket
Top 25 teams: Five (2, 7, 13, 18, 22)
Top 50 teams: 7
2nd 50 teams: 5
Sub-100 teams: 4
Bottom left (Rochester) bracket
Top 25 teams: Four (6, 8, 9, 17)
Top 50 teams: 9
2nd 50 teams: 4
Sub-100 teams: 3
Top-right (Nebraska Wesleyan) bracket
Top 25 teams: Nine (1, 4, 5, 11, 12, 14, 16, 19, 24)
Top 50 teams: 10
2nd 50 teams: 4
Sub-100 teams: 2
Bottom-right (Augustana) bracket
Top 25 teams: Five (3, 15, 20, 21, 25)
Top 50 teams: 10
2nd 50 teams: 4
Sub-100 teams: 2
It's pretty clear which one is the toughest (though it could have been worse this year.)