You can get the wild mage in beregost, north from the smith, near the mayor's house. ( edit) More precisly north west from silke.And for the new characters, does anyone know where you find them? I spotted the Monk in Naskhel, but I don't know where to look for the Blackguard or the Wild Mage.
I got the blackguard by first talking to him in friendly arm after fighting against Tarnesh (He doesn't join you just yet) and when traveling to Nashkal mines I encountered during Random(?) encounter