It might be ask as well if Sidious' and Yoda's final part of duel, a lightning sequence wasn't brief? It was, and it was enough for Sidious to be able to gain a tmporary advantage and enough for Yoda to retake it.
In that case it seems to be longer. They starts fighting, Talzin saids somethink, then Sidious, then we see them on equal terms, then we see Dooku getting up and taking his saber, then them fighting as equals again, then Maul who finally supports Talzin with his energy, and the Dooku join the fight and he and Sidious overpowerd Talzin who is forced to use her shield (impressive as hell). I would say, that it was far longer then Sidious vs Yoda (only a final part).
And where to place her... It was said that Dathomir was a "hearth of Mother Talzin's powers" (or something like that?). And that she didin't restoerd her fill powers yet. After taking a Dooku's body and after leaving it under the pression of Sidious FL, she declares that she is "whole" (again, if I'm correct, I don't have a comic at the moment). I would asume, that she was at her 100% at the end. Perhaps she drained a lot of Dooku's energy, idk. So:
100% Talzin on Dathomir, a place declared as her nexus was more or less equal to Sidious. Aside of Dathomir, she could only be his inferior. But how inferior to him she would be? Impossbile to tell for me.
Before being arrsted, Dooku declared to nightbrothers that he will kill them, then Maul and then Talzin. At this point, I guess he and Sidious had that in mind that Dooku will be a bait for Talzin. Was he really meant that he could beat her? And even if, was he right? Hrd to tell. Weakened Dooku was much of a factor at the end of the fight - still, his support gave Sidious far more then Maul's support gave Talzin. Adding her with with Mace... I agree with Thor that she would be somewhere near to Dooku/Mace.