What is the scope of HR and marketing (dual specialization) for MBA especially for those having good communication skills?

Yes, recent trends of management are inclined towards dual specialization. You can do that but try to take your subject electives regarding those area and be up to date in those sectors.

Good communication skills can open growth for anyone doing anything. However, HR and marketing seems different to each other. Doing major in one of these and minor specialization can give you an edge.