to the Farm? IIRC Semirhage sent the Trollocs to the Stone in TDR. But I think Graendal may have sent the ones to the farm in one of her side plots to make the others think Asmodean was still alive and masquerading as another Chosen.
This tidbit in the Companion support this idea
Yes it suggests she blamed Asmodean for things, but I see no direct evidence of the attack on the manor house. Remember too that the Forsaken was disguised as Sammael, not Asmodean. It's a pity we'll never know about this.
Guess it's one of those things we'll never really know ... I suppose I just tend to blame such activity on Graendal because it seems to have fit with her general desire to have Rand killed, but wanted to stay as far away from the blame as possible. The Sammael disguise was clearly a disguise and seen through rather quickly which leads me to believe Graendal wished for the others to believe Asmodean had disguised himself as Sammael in order to send the Trollocs. Convoluted enough to be one of Graendal's schemes 
I read AMOL today and I saw Moghedien comment that she had become proficient at imitating all the Forsaken.
I suspect her mind trap would give her away
