Whats to stop Egwene from traveling to Elayne and using her bond with Rand to track him down? I thought that the reason Elayne and Aviendha did not travel to the cleansing, was because they were worried that Rand would think they were attacking and strike at them. And Aviendha was correct in this.

However that would hardly apply in a normal situation where Rand&Co are not performing a huge channeling task and expecting attack from the forsaken. There might be wards to detect "unauthorised" traveling around Rands camp, but I very much doubt the first reaction of the AS/Asha'man would be to attack in a peacefull situation. Especially once they see its a pregnant woman.

Or what about using Need? I cannot see much more important than "Needing" to find Rand to warn him about black ajah that could assassinate him at any moment. Egwene is skilled in dreaming and could locate Rand's position that way. Or she could try and contact Nynaeve's dreams and warn her, since she knows that Nynaeve is with Rand. She has done that before.

Or what abou the wise ones? Egwene could contact them and they could warn Rand. Elayne knows that the Aiel (including the WO) left to join Rand afterall. Or Egwene could find the dreams of other of Rand's allies such as Bashere or such and transmit a message that way.

Egwene could easily contact Rand with just a little time and effort, if she thought it worth it. But apparently she does not consider warning the Dragon Reborn important.