Infallibility are not worthless at all on mages.
I don't know the exact mechanics, but putting it on Shayd greatly increases damage to WBs during Banish. Most people attribute this to either making her stun more of miss less.

Infallibility on Smoulder, Djehuty, or Mulan makes a noticeable difference in how much damage they deal when fighting other players.

Not sure if they help other mages though. Maybe it helps Queen Bryn stun and hit more as well? Most likely they won't offer any benefit at all to the blue and white mages.