I'm not worried. Evoker is currently garbage at 1v1 PVP in the beta, everybody beats them, everybody has more tools than them for PVP. They're very similar to elemental shaman.
They have some kind of insta nuke gimmick like in the video below, but if they can't kill you with it, they're done.
They may be a threat in arena but I don't do arena PVP, so I don't give a shit.