[Leigh Butler]
From [LOC: Prologue, The First Message, 58]:
Semirhage: "I am still waiting to hear what the Great Lord said."
Mesaana: "Yes. Are we to kill Al'Thor?"
Demandred: "...The first part of the Great Lord's message was simple. 'Let the Lord of Chaos rule.'"
Aside from the obvious interpretation of this command (namely, "go out and sow chaos"), it became clear over the course of LOC and ACOS that it also meant that, to this end, the DO had laid a prohibition on killing Rand. From that point until the end of TPOD, no Forsaken except Sammael made any direct attempt on Rand's life - and Sammy's attempt was foiled by none other than Moridin, Mr. Nae'blis himself (Moridin was the Wanderer - see section 1.2.3).
This prohibition was apparently not lifted until the Forsaken Coffee Hour in WH. Cyndane tells the FS that Rand had the Choedan Kal and planned to use them to try and cleanse saidin. Then: "'So it seems he must be killed after all,' Demandred said... 'Killed?' Moridin moved his hands as though weighing something. 'If it comes to that, yes,' he said finally" [WH: 13, Wonderful News, 318].
Seems pretty straightforward, right? Except for one thing - the attack on Rand in TPOD. If the prohibition on killing Rand wasn't lifted until WH, then why did one Forsaken and at least two Darkfriends try to kill him in the previous book?
WH answered some of our initial questions about the TPOD attack. For one thing, Dashiva's identity is cleared up - he was Osan'gar [WH: 35, With the Choedan Kal, 645]. For another, Gedwyn and Rochaid (and Torval and Kisman) were definitely Darkfriends, and Taim definitely ordered the attack [WH: 22, Out of Thin Air, 441]. The rest of it is not as clear-cut. What appears to have happened, from Demandred's POV during the Coffee Hour and Kisman's POV in [WH: 22, Out of Thin Air, 441-443], is something like this:
Taim calls in the Fearsome Foursome and sends Gedwyn and Rochaid to Cairhien, ordering them to kill Rand. G and R arrive in Cairhien and blast Rand's rooms apart. At some point during or after their initial assault, Dashiva/Osan'gar joins them, evidently with the intention of taking advantage of the situation to launch his own attack on Rand.
G and R miss Rand, of course, and after wandering around for a while Rand finds them arguing with Dashiva. Dashivan'gar sees Rand, snarls, and fires something extremely lethal-looking at Rand, who blocks it by channeling some kind of super-shield around himself. He gets knocked back down the hall, and the perpetrators use the opportunity to escape. (Kisman notes in WH that Dashiva - whom he obviously never knew was Osan'gar, by the way - had disappeared after the murder attempt, so we can safely assume that he went off alone, rather than wherever Gedwyn and Rochaid took themselves off to.)
Mere hours later, Taim shows up in Cairhien. He tells Rand (calmly) that Gedwyn, Rochaid, Torval, and Kisman have deserted. Rand tells Taim to add Dashiva to the list; the news that Dashiva participated in the attack seems to shock and anger Taim quite a bit. Then Rand sends Taim away and goes on the lam with Min.
So much for sequence of events. It's clear that Dashiva/Osan'gar really did intend to kill Rand in Cairhien; Kisman's POV in WH tells us that Taim did, in fact, order Gedwyn and Rochaid to do the same. What's not clear is whether G & R were intended to succeed. Kisman thinks to himself that he was unsure, despite Taim's point-blank order, that the Fab Four were actually supposed to have killed Rand in Cairhien. Taken at face value, the attack was not orchestrated very well, and Taim must have known that Gedwyn and Rochaid were no match for Rand unless they had the advantage of surprise, which they promptly lost by destroying Rand's rooms - after he had already left them. (Dashiva's strength is not a factor, since Taim had obviously had no idea that he would join in the attempt.)
What it all boils down to is this: Why did Taim order an assassination attempt that seemed almost designed to fail, and why did Dashiva/Osan'gar use the opportunity the attack provided to violate an order passed down by the DO himself and enforced by Moridin, of whom Osan'gar was terrified?
Well, maybe he didn't. Consider: why was the order revoked in the first place? Was Cyndane's information - that Rand was planning to use the Choedan Kal to cleanse the Taint - the cause of the reversal, as we have assumed so far? Or were Moridin's words at the meeting in WH merely confirmation of what had already been decided?
Recall that Dashiva/Osan'gar (and the Fearsome Foursome) found out Rand was planning to cleanse the Taint in [TPOD: 14, Message from the M'Hael, 306], long before the Coffee Hour in WH. What if this revelation was enough to decide the Forsaken that he had to be killed? It's clear from Demandred and Osan'gar's conversation at the meeting in WH that they had been searching for Rand rather desperately ever since the attack. Osan'gar even says, in reference to the failure at Cairhien, "'Simply probabilities... Next time, he will be killed or taken. Chance can't protect him forever'" [WH: 13, Wonderful News, 314]. This is before Cyndane talks about the Choedan Kal, and before Moridin says to kill Rand if necessary. Would Osan'gar have talked so openly about something that was still forbidden at that point? It doesn't seem likely, any more than it seems likely that Osan'gar would deliberately disobey the DO's order in such a public way as helping blow up half the Sun Palace.
So the evidence seems to indicate that the prohibition on killing Rand was removed prior to the TPOD attack, after Rand spilled the beans about his plan to cleanse saidin, and the information about the Choedan Kal from Cyndane just served as affirmation to Moridin that this was the proper course.
The only real sticking point in all this is Demandred's phrasing. He says "So it seems he must be killed after all" (emphasis mine). Not "So we are supposed to continue trying to kill Al'Thor" or "We are to try again" or something similar, as would seem logical if the order had already been revoked [Joseph Slonimsky]. This is kind of puzzling, considering he had been raging a few moments before about how "those blind fools - those idiots! - failed in Cairhien." Note, though, that Demandred being pissed about it doesn't necessarily mean he had anything directly to do with the attack or even that he wanted it to succeed; it's an ambiguous statement. It could be interpreted as meaning that Gedwyn and Rochaid and Dashiva/Osan'gar were idiots for even trying it.
One possible way of explaining the "after all" phrase: maybe the order before the Forsaken Coffee Hour was something like "capture him if you can, kill him if you have to", as Osan'gar's comment above seems to suggest, and that Demandred's question meant "so we forget about the capturing part and just kill him?".
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. Regardless of his allegiances, it is unlikely that Taim's order was motivated by Rand's slip about cleansing saidin (see section 1.5.6 for why). So, given that, 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 channelers 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.