Better than her performance in Warlord? I have to disagree with you on that. I thought she went above and beyond in Warlord; she was nasty, cruel, and extremely seductive. Playing the villain gave her the chance to show audiences what she was fully capable of.
I too think Warlord
was Jennifer Lien's best performance. She's usually good in episodes that revolve around Kes but I've always felt her range was never showcased better than when she was playing Tieran. This episode more than any other makes me regret the loss of Kes/Lien to VOY.