Let's just hope Una will make Ezri less of an arrogant know-it-all. From the first relaunch novels, novel-Ezri has not been a very good character to me, even though I really liked Ezri in season 7 of DS9.
I'm not sure "arrogant" is the right word there. To arrogate something is to assert a status or privilege to which one is not actually entitled. Dax has lived for over 300 years, done many different jobs, and been joined to a number of brilliant individuals. So any Trill who's joined to Dax is going to know, if not "it all," then certainly an exceptionally large percentage of "it." She's not just putting on airs, trying to act superior; she really is that smart, and she's just using what she's got, rather than resisting it as Ezri did in her first year as a joined Trill.