I really think we are underestimating the utility of Traya's assassins. Sure they aren't as effective against non-Force users as they are against Jedi, but that does not automatically void them from this battle. They are still effective. They can still 'backstab' people or infiltrate areas. In fact, I think they could get on G0-T0's ship. Provided that he is still preying on shuttles around Nar Shaddaa.
I don't see them finding the ship. If they can't find an organic who has no force connection- how can they find something with absolutely no force energy? Even if they do find the ship- they would be annihilated. These assassins rely on a force ability that makes them stronger when their opponent is stronger in the force, and vice versa. With an opponent who has no force abilities they would be destroyed. Literally.
And to Beni- your right- Traya will most definitely not be on Malachor V. With the MSG and barely any defense* she would be severely out matched there. But if she leaves she loses her Dark Side Nexus and some power. Would she take the risk? Yes- but where would she go? Does she have Dxun?
* Assassins being incapable of winning.