I've only obtained Asteria Mitts+1 so far but here's what I see with Carbuncle wearing only Nirvana, Seraphicaller, having 550 Gifts and no food active.
Without Asteria Mitts+1
Primary Accuracy: 970
Primary Attack: 849
Evasion: 704
Defense: 743
With Asteria Mitts+1
Primary Accuracy: 1007
Primary Attack: 879
Evasion: 727
Defense: 766
I'm guessing that in order to take advantage of any benefit whatsoever with Carbie's level 122, the Mitts would have to be full-timed. Testing and confirmation needed to verify, of course.
I haven't tested any BP's or Wards yet. I have Lamassu Mitts but also haven't tested those yet.