The Blackbirds led 64-63 on Elvar Fridriksson's 3-pointer with 2:26 left, but Joe Bramanti made 1 of 2 from the line with 16 seconds left in regulation to tie and Fridriksson's last second 3-pointer missed.
Brooklyn raced to a 13-4 lead over the first 5:24 but New Hampshire roared back, closing the half on a 14-4 run - and a 6-0 spurt in the final 53 seconds - to trail by one at the break.
Fridriksson finished with 19 points and Hermannsson had 15. Landon Atterberry added 16 points for the Blackbirds.
Armstrong paced New Hampshire with 18 points and Jaleen Smith added 13. Leissner had 10 points and 11 boards.