HEP B.A. course deals with history, economics and political science which are very good subjects for studying civil services., but I say studying only these subjects is not important for civil services as civil services deal with every aspect of the country.

The best course to pursue IAS is humanities and also in general studies of every subject such as history, geography, politics, public administration, economics, ecology, environmental sciences and also ethics.

Every subject is important for studying civil services., So no matter which subject you choose having grip on every subject is  important.

Hope this information is useful to you.