Well, Kurama normally "plays with his opponent" to get a feel of how he moves,acts,etc. That might not be too great of an idea in this battle as it will be messy and quick. Also, most of his higher level attacks are kind of slow to take effect, and he might die before anything takes effect. Slow would be seconds of course, but every second counts with these guys. Of course, it's not all about a solid plan, Yoko is also about on the spot trickery, and that could be effective here, especially since they really don't know what he's capable of and that he has more tricks up his sleeve than either of them. I see Hiei being able to take Byakuya or Toshiro alone. He might be able to kill one and then he and Kurama could tag team on the other. Reading people's minds helps too, if Kurama has a plan, he'd know instantly. Hiei could easily amp himself in this battle, with them not knowing he can do that, and the fact that they're are going to try to avoid the big scary blackfire dragon thing, I see one guaranteed amp should he want to use it.
I'll throw myself out there and say 7/10 in Hiei and Kurama's favor.