Mintz said the two were exciting signings for the team.
"Joe's got some massive power and can play third base very well," Mintz said.
"Blaine is a very, very fast young man and has some massive pop too for a little guy. He's small in stature but he carries a big stick."
The duo join Kiwis Max Brown, Beau Bishop, Scott Cone, Jimmy Boyce and Daniel Lamb-Hunt, and fellow imports Josh Collmenter, and Eric Jenkins on the roster.
The team will also carry 17 development players, who trialled for a role with the team at the weekend.
Initially looking for two players to take a spot on the Tuatara roster, Mintz decided all 17 would be taken on as development players and would play some sort of role with the squad through the season.
Baseball New Zealand director Brett O'Riley said based on the talent they saw at the trials, the side might not need as many imports as initial thought.
"We had a couple of guys throwing 90 miles per hour yesterday, so that's really encouraging.
"We're already a year ahead of where we thought we'd be."
Tuatara development players
Andrew Marck, Kris Richards, Takahiro Kaneka, Luke Hansen, Marko Lezaic, Yuuki Takahashi, James Hill, Sage Shaw-Tait, Dante Makea-Matakatea, Matt Boyce, Mitchell Finnie, Nao Fukuda, Correze Nepia, Elliot Johnstone, Duncan Izaaks, Keegan Swanepoel, Seth Gibson.