Regarding the sa'angreal issue, Egwene al'Vere does not share power. She is kind of ego-centric, so letting someone else have the rod to increase the power of the circle is probably not as important to her as having the rush herself.

And of course, there is always the VERY strong possibility of a mistake on Sanderson's part. The book is rife with them, from misprints such as Rand putting his head in his handS, to uncharacteristic dialogue, to various continuity errors, to such egregious flaws as Bael making a reference to "the Waste."

As for the Elayne thing, it is later stated that her issues with the dream ter'angreal has nothing to do with channeling! RtDB. In KoD, she gives the stone ring (NON-channeling) to Aviendha when the latter leaves Caemlyn, saying it was useless to her since she became pregnant. She CAN use the dream ter'angreal that require channeling, when she can manage to touch the Source. It is NEVER stated that the failure of the stone ring to work for her is attributable to her channeling difficulties. It is IN SPITE of her channeling problems that she keeps the sleepweaver which requires channeling and gives up the non-channeling stone ring to Aviendha.