WH
With the CK

Using the full strength of her circle, she wove her shield, and watched aghast as it rebounded. The woman was already embracing saidar, though no light shone around her, and she was immensely strong!
Then she had no time for thought of anything as the golden-haired woman spun around and began channeling. Verin could not see the weaves, but she knew when she was fighting off an attack on her life, and she had come too far to die here.

You are correct that it's seen as weakness, but it clearly doesn't mean it doesn't happen... we've seen plenty of examples of even experienced Channelers doing this, even though it's open talked about as being bad form.

AS clearly perform way more weaves including gestures than other groups, but we've seen it from others as well ...

WH
With the CK


Abruptly the light of saidar appeared around the woman, but the ready ball of fire streaked from Cyndane's hand, small enough to escape detection she hoped, but enough to burn a hole through this woman who—

The Asha'man training includes gestures too it seems as we've seen on a number of occasions:

WH
With the CK

Abruptly the old man stopped and thrust out his hand straight toward Demandred, and Demandred found himself frantically fending off a net of saidin that struck his warding much harder than it should have, as hard as his own spinning would. That tottering old man was an Asha'man! And at least one of the women must be what passed for Aes Sedai in this time, and joined with the fellow in a ring.

Everyone seems to raise their hands in some form or another for Balefire, and Lightning as well as Fireballs ... all the "aggressive" or "combat" weaves seem to have some form of gesture. We don't see a lot of examples of anyone weaving combative weaves without aiming with their hands ...

at any rate it's pure speculation on my part as it seems like in most cases there were no Wards set up and the odds of Verin having Ta'vern luck on her side against Graendal are pretty slim...