I have twice, in all my hours of playing, had 2 raids happen within minutes of logging in. I always try to log out at night in my house so I can sleep when I log in and get the rested buff. I have read you shouldn't get raids upon logging in but maybe it was so close when the logout happened that it just happens. Either way I welcome the free drops when its done. Just a note I have not been to Mistlands yet nor in any map or playthrough killed Yag.