Short forms always work in spoken as other languages do, and I think "~ 하는 거예요?" is often found in textbooks to explain how the Korean language works in terms of grammar. This kind of the style of the speech is more prefered by women, I think.
In daily conversation, "뭐하세요?","뭐해요?" and "뭐해?" are often used.
It's my two cents.^^
\^o^/