It only makes sense that there might be other super strong channelers e.g. in Shara, in the Land of the Madmen or among the countless other damane, who will never appear in the series and are not on the list. Therefore your apparent belief that Alivia must be the strongest damane who the Seanchan had, just because she is the strongest damane we saw yet, is pretty absurd.

Furthermore, Tuon goes to war. And she states in WH that she took her best damane with her to the Westlands. Certainly those damane aren't just meant to make nifty fireworks, but are a powerful guard. Tuon explicitly mentions Sera's great OP strength as the important factor, why she chose her. And you can't seriously argue that the Seanchan wouldn't generally praise stronger damane more than weaker damane.

As said, maybe Tuon's other damane aren't stronger than Alivia, but it would be quite surprising if Sera isn't stronger than Alivia. In any case, I definitely think it's a mistake to ignore or dismiss Sera in the discussions about OP strength like you apparently want, since it's obvious that she might be among the strongest female channelers around.