When Adelorna sees Egwene unclasp a damane's collar, she says the weave moves with "dexterous speed". Egwene then shows Adelorna the weave, but warns her that is generally much easier to just kill the damane.

I think it looks so simple to us because it was Egwene doing it. Her strength is obviously far above the average Aes Sedai's, and her dexterity has been shown to be downright phenomenal. Other Aes Sedai might be able to do it if they sneak up on a damane, but in a firefight, trying to free the damane will just get the Aes Sedai killed.

However, that doesn't really put them at a disadvantage, since the other options are shielding or killing, and those aren't terribly hard for linked circles. And I guess if they manage to shield the damane, and kill any soldiers with them, then they can take the time to undo the collars, though that will mean they're burdened with a lot of prisoners who will be catatonic at best, and fighting them hysterically at worst.