Customer reports Deus Ex wouldn't launch in Crossover 15 until they applied patch http://www.moddb.com/games/deus-ex/downloads/patch-to-v1112fm
You can apply a patch by downloading the patch .exe and doing an unknown app install https://www.codeweavers.com/support/wiki/mac/mactutorial/unknown_install into the existing bottle containing Deus Ex.