Why did Taim order the attack?
Kisman’s POV tells us Taim ordered the attack and confirms that the four Asha’man are still working for him, so there’s no longer any question about that. Making no assumptions about Taim’s true identity, what did Taim have to gain from ordering such a lame-assed assassination attempt on Rand? Well, if you think about it, it’s a win-win situation for Taim whether the attack succeeded or failed. If it succeeds, well, Rand’s dead, leaving Taim free to seize power at the BT. And if it doesn’t succeed, Taim gets a group of male channellers who are loyal to him, not to Rand, and whose actions Taim can disavow, plus the credibility to claim their desertion to Rand and be believed. Rand doesn’t trust him at all; if Taim had simply shown up and reported that his four most trusted lackeys had deserted, Rand probably would have been immensely suspicious of the whole state of affairs. However, after the attack, Rand doesn’t even question Taim’s word.