That Vindicare assasin cannot catch a break can he. I'm sure if someone used him effectively in a game against you, you might change your mind.
As for Callidus, I've used her three times.
*First time I used her, I moved a rhino so we could shoot a Balalisk behind it. Turned out okay, we blew it's weapon off (unfortunetly the Chaos player doesn't know his own rules, so he grew back the weapon at the start of his turn). After that she came on, I forgot about her and she got killed
.
*Second game I moved a Broadside out into the open. Wasn't much I could do. She killed a whole Fire Warrior squad and soaked up quite a bit of firepower, so I was happy.
*3rd game, was in a Carnage match. She did very little. She died without killing anything.
Still, I'd choose her over the other assasins, her rules are just awesome. As for the Eversor, used him once and he owned