I think it will eventually come down to tactics. The game is very rich in tactical maneouver description, and each holds advantages and disadvantages of its own. That´s another thing I love about Amber, there is no "Intelligence" or "IQ" or "Reasoning" value, so tactical thinking will fall onto the player. I know that actually the "tactical" part is covered by the warfare attribute, but in the given example, we can assume that being outnumbered by characters with high warfare themselves, the advantage of Mr. W=30 can be considered nulified to the point were what can save him is a good idea. Remember how Corwin beats Benedict, he is inferior, he knows it, and his rival knows it too, as a tactician as well as a swordman, but he manages to bring him down with a good idea. So, let's assume Mr. and Ms. Dummie frontally and directly attack Mr. Big Dude. Well, IMO he wouldn't have problems in the medium-to-long range to chop them down. But maybe Mr. and Ms. Dummie go for a flanking maneouver, or one goes all-out and the other only tries to disturb Mr. Big Dude, or their geographical position is superior (aka they've got higher ground), or they manage to take him to a terrain that's favorable for them... then Mr. Big Dude may be in trouble. In the other hand, Mr. Big Dude could try to concentrate the attack in the one he judges weaker to kill him fast, or could run for the hills in the hopes that if they follow him one's faster than the other so he can take on them one at a time, or, an all-time favourite, role-play his way out of the pinch.
And, if anybody followed my broken english all the way here, I'll just say I think it is a matter of common sense. And of course, the most important rule of it all: setting dirty corwinesque tricks aside, First Place wins. He may just tie against two one point fivers, but that's about it.
My hands hurt.