Sekhmet's basic attack benefical effect removal

[Liu]

Would someone care to explain to me how this works exactly ?

In the skill description it says "Remove One Beneficial Effect from each enemy". From this I infer it removes one blue effect with 100% chance (from each opposing toon). If there is more than one blue effect, one is selected at random and removed. The duration of the effect should not matter. Do I understand this correctly ?

I use her quite a lot and I've noticed that it doesn't work in the arena quite properly. The chance is not reliably 100%. At first I thought it may correlate with effect duration, i.e. when the effect exceeds a duration of 1. but maybe it is related to the presence of golden effects ? if a golden effect is present, and randomly selected as the one to be removed nothing happens as she can remove blue effects only ? I don't know, I've got to observe more I think ... Did anybody else notice this ? Am I overlooking something obvious ?

update:
So apparently it's never working when perfect immunity is present. Is it supposed to work this way ? Not sure if the same is true for "regular" immunity, will post an update once I'll get to see it.