Graendal didn't need her angreal when she (literally) humbled Cyndane and Moghedien. She didn't even have surprise on her side, because Moggy was holding the Power already, and both women initiated the attack in the first place!

If, without really needing her angreal, Graendal can beat two of the Foresaken, one of them even stronger than her, she is indeed someone to look out for.

I don't know what your issue is with women being as strong as men. Did some girl hand you your ass in a fight once? Because you can yell that women are weaker till you're blue in the face, but the fact remains that RJ said they can match men in every way, and has shown that multiple times in the series.

And all evidence indicates that Graendal is just two levels below Lanfear, and had no worries challenging her openly in tFoH. I don't see the logic of putting people like Rahvin, who was more than two levels below Ishamael, above Graendal.