I think Graendal just stood there and let the shield bounce off. It was an absurd attempt by Verin who couldn't even sense how much saidar she was facing. It's actually kind of atrocious that this circle did as well against Graendal as all the Light's strongest women did against Hesselam. Who wrote this stuff!
Possibly she did nothing, or she could have forced it away as we heard Adelorna talk about during the Seanchan raid. Most probable, IMO, is that Verin created a shield strong enough to shield a very strong woman, but Graendal was boosted to Male strength levels and thus it failed.
The only thing I can think of as far as why Graendal showed so poorly is that she was only at the Cleansing under direct orders. Whereas in the Last Battle, she knew this was THE Last Battle ... it was win or die basically ... at the Cleansing she had fewer resources to draw from and could get away with a strategic withdrawal when massive Callandor driven attacks were coming at her too.
Perhaps the big difference was the Light's lack of "air cover" in the Last Battle ... the roles were nearly reversed with the Light having to contend with massive attacks from Sakarnan being directed toward them and the Forsaken being able to attack from a less defensive position?
I agree! Asmodean not being able to break through a tied-off partial shield was an anomaly IMO ... but then he was shown as particularly inept most of the time. Honestly, he was also a poor teacher and was even worse with weather than Semirhage, and showed no particular skills with the OP that we saw. How did this oaf end up as a top ranking Forsaken when he was so easily contained?