I have a similar but not identical issue. I'm at 16/17 motes. I have all of them from cysts. My triumph for tracking which bosses I've killed seems to be bugged, as it says I've killed them all. I have since went back and rekilled all 3 in the impasse and blooming. I absolutely cannot get the arc wizard to spawn in the landing. I've done probably 11 overthrows there now and no luck. I've been told it's a rotation and to just stay and kill them all in one instance, but this isn't working for me either. I just get the void knight spammed at me on repeat with occasional appearances by the solar acolyte. This is growing increasingly tiresome and frustrating. Would love some clarity on this obnoxious malfunctioning pursuit.