On all the computers I've used so far, including: Windows[8, 8.1] , OSX[Mavericks,Yosemite], debian[wheezy], ubuntu[14.04.1], I've seen the same problem: the org-entities symbols for phi and varphi were inverted, and the symbol for setminus was displayed as a W with a strike-through.

Attached is a patch that exchanges between the inverted symbols, and replaces the W symbol by the unicode 'SET MINUS' symbol.

Thanks,

Kosta