It"s true that Yellow-browed Warbler can sometimes show a faint crown stripe, but I think it tends to be more diffuse than in Pallas's, less prominent.
The supercillium of your bird is very broad and yellow, reaching the forehead. I would expect it to be less prominent in Yellow-browed in comparison.
http://ibc.lynxeds.com/photo/yel ... llow-browed-warbler This bird shows a diffuse crown stripe. Note the (white) supercillium in front of the eye.
http://www.freewebs.com/suffolkbirding/october2011.htm. Same goes for the supercillium here. Compare it to this Pallas's:
http://www.portlandbirdobs.org.uk/latest_oct2010.htm and also note the dark eye stripe.
But anyway, if you saw a yellow rump, that would exclude Yellow-browed all together.