I'm okay she finished off Mesaana. Despite Brandon's utterly incoherent writing, and the insane justifications for Egwene not being at the top of her game in TAR, it was pretty clear Egwene would be taking down Mesaana, and it happened, though not well.
For me, Egwene's greater achievements always lay with the Tower, and with Rand. And she did effective, important work killing hundreds of thousands of Trollocs during the Last Battle, and led the Aes Sedai to kill many more.