For someone like me who has never really been a keybinder, DPS is quite difficult for me to master. Very difficult actually, because I have never keybinded and its hard to grasp it.
Although for healing I feel that I can do excellent. For the most part being due to all of my heals and targeting is done on healbot using my mouse. My trinkets and CDs and done with 1-5 mainly with left hand so it makes it very easy.
But with DPS, you have to bind EVERYTHING for your left hand.
I guess if keybinding is easy for you, then thats great. But for someone like me, I find healing 10000 x easier in PVP.