I know that autocomplete widget with profile2 searching problem already solved in 7.x-1.x-dev
but I found other problem in user views with profile relationships.
when I made profile views with user relationships there is no problem.
but when I made user views with profile relationships I coudn't search any related value with profile in autocomplete widget.
only worked in users original values.
there are steps this bug report.
1.make user views with profile relation.
set entity reference display with profile search fields.
2.make field that is referenced entity. and set user , views mode. and set autocomplete widget.
in these settings, you can't use autocomplete widget. searching doesn't work.