Thanks for providing Moghedien's actual comment on Hessalem's strength.

The way it reads, based on your quote, seems to imply to me that Graendal is saying that she is suprised that someone of Graendal's strength was not picked up by her agents, given that they picked up Nynaeve so quickly.

Meaning that if Nynaeve was discovered, then someone even stronger than Nynaeve should have been discovered even sooner.

Granted, Moghedien thought, sitting, she is powerful. How had Moghedien missed noticing one with this talent among the Aes Sedai? Her sources had picked out that wretched lightskirt Nynaeve almost immediately, yet they'd missed this hag?

Anyway, that's how it reads to me. But I don't have the exact quote and context in front of me, so I guess it can be interpreted to suit whichever viewpoint one holds on their comparative strengths, other than one which holds Nynaeve to be stronger than Graendal, which we know is not the case anyway.

Any more on Moghedien's reference to Taim's strength? Howcome she knows how strong he is? She can't sense male strength. So who would have told her he is fairly strong?

Taim... M'Hael... was said to be strong, perhaps as strong as the rest of them, but elevating one from this Age, with all of their ignorance.... It galled her to consider that this M'Hael would be regarded as her equal.

Also, she doesn't seem to think that he is as strong as the stronger male Forsaken. Merely that he might be as strong as "them", which includes herself, the weakest of the Forsaken by some margin.