Graphics problem with Inspiron 5537

My Dell Inspiron 15R 5537 have a dedicated graphics card of AMD Radeon HD 8670M along with integrated Intel HD Graphics 4400. The laptop is installed with Windows 8.1 64 bit OS.

My windows experience index is 4.6 due to low graphics performance. So I updated the driver from AMD to latests the Dell provided drivers were old. Now the score has increased. But my laptop lost the ability to wake up from Sleep/Hybernate modes. I rolled back the drivers and Sleep/Hybernation work fine now. But my graphics performance is low. With Dell drivers, laptop is not using Dedicated graphics (checked in dxdiag).