My guess was that now of them was in ideal situation to use their NP, lets break it down.
Karna - Bramaestra has a very big range so it makes sense he wouldn't use it in such a confined place and not only that but in his own base. The fight also wasn't that desperate enough for him the VS
Avicebron - He didn't have his completed, also he didn't really have any combat abilities other than the golems he was using.
Achilles - He doesn't have any offensively strong NPs other than his chariot, so that counts him out.
Atalanta - She has already used her NP two times before so there could have been some energy constraints, also the fact she was also in a closed in room also limits it since it comes from the sky.
Chiron - similar situation to Atalanta in that needs access to sky,
Jeanne - Her's is a defensive barrier not something to attack.
That's what I think was the circumstances about it anyway, I could be wrong on a few things and in retrospect this is really just excuses than hard facts.