If your doing WordPress than great designers can developed it too. I know plenty of graphic designers. If u need a couple DIFF leads I can send u some options.
Yes, and then a few months down the line you are wondering why your website is so slow and is a pain to maintain, and then you find out why designers are not developers too.
If you're buying a theme you should be okay, but if someone's writing you a theme from scratch you are much better off paying a good programmer to do that.