For Sidious, when Alivia faced Cyndane, Alivia was by far the stronger because of her angreal , and had various tools ( ter’angreal ) to work with besides, but Cyndane was much, much more knowledgeable about channeling. Alivia, after all, knew relatively little except how to be a weapon. That was very useful in the situation, but in this case, knowledge versus strength made it an even match.
Now as to Rahvin sitting on his throne and being shocked to see Rand. First off, he knew his first trap hadn’t worked, but he had others ready. He saw no reason to start jumping about. He thought he was maneuvering Rand into a series of traps, one of which he was sure would work. He did not expect Rand to simply leap into the same room with him. He did not expect Rand to know that he could Travel to somewhere in sight of himself without knowing the ground. So what he had expected to be a chess game where he knew the positions of all the pieces and Rand did not suddenly turned into a close-quarters slugging match. Surprise!
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