But Elminster did know. Remember 'Terminsel' who turned up during the game? Yes, he lets the PC know that Jaheira has gone back to Harper Hold. But he didn't in any way let Jaheira know that the Harpers under Galvarey were frauds, he didn't offer her so much as a word of comfort, instead he kept manipulating her, and in the very last encounter she's supposed to 'justify' her actions to him.
No, while I know that there are some people who feel for the old coot, I'm adamant about this. As far as I'm concerned, Elminster is a bastard. 
Alright, granted, he knew, but how does that make him "manipulating" her? I don't get it. How can you honestly say Elminster wasn't short on time and had only enough time to give the PC a heads-up? Besides, Jaheira was out of the party when he gives the note (which he claims to have found blowing in the wind), how could he have given her words of comfort??? Also, Elminster--at the end--is letting Jaheira judge the worth of her own actions, he isn't asking her to "justify" her actions to him. It seems to me as though you are seeing this in the worst way possible.
And, simply put, Elminster is not responsible for the mental well-being of Jaheira or the PC or anyone else. To imply that he should be is absurd. As I said, he can't be everywhere at once, and it's not like he does nothing--there are always important events (involving bad guys) that need his attention. The fact that he gives the matter attention at all shows geniune concern on his part, in my opinion. In no way is he *obligated* to help you or your party. Elminster is a believer in helping others, but also letting them solve their problems on their own (and thus, learning).
It really does seem to me like many of the people posting in this thread don't really understand Elminster, or have a lot of misconceptions about him. Userunfriendly even admitted that she (he?) never actually read novels or books about him, and that her opinion is based on how he acts in the game. Is this fair? I agree with Mikka that it does seem like this mod may become a vechicle for "Elminster abuse" just because the creator happens to hate him.
PS: If Edwin showed up at El's house trying to kill him, then he deserved what he got, I'm sorry. By the way, Edwin got it easy. His gender was changed, but he didn't end up a pile of smoking ashes as do most of the Zhentarim/Red Wizard agents who show up trying to kill him. What do you expect El to do other than defend himself?