Here are some more pictures of the mystery warbler. I am inclined to call it a Yellow-streaked Warbler due to the call notes. I listened to Radde's Warbler call note and they sound wrong--this bird really did sound more like Arctic than Dusky. I can't find a recording of the Yellow-streaked Warbler call. If it sounds like a Bunting, then which bunting species is closest?
With regard to behavior, it was indeed on the top of some smaller bushes with climbers but then flew into middle canopy of some nearby trees. I was on a hill so most shots will look eyelevel.
I have more pictures but I am at my 800kb limit.
What do people think?