Rockers take getting used to. I tried rockered boards for the first time this year when I demoed 2011 boards. Needless to say, it was pretty damn different.
I had similar problems that you are experiencing, but only on steeper and faster runs. This is where a lot of rockers suck. They just aren't meant for riding on hardpack/icey steeps. Rockers are great for freestyling and powder riding. Now, some rockers are combined with various tech to tackle those above mentioned issues. Mervin Boards (Lib Tech, GNU, Roxy, Rossignol) did a great job with combining some of their rocker boards with their Magnatraction. Magnatraction owns the hardpack/ice.
Another issue you need to consider is the height of the rocker. If you get a rockered park board, then the rocker will be higher which means it is harder to engage the edges. This is very useful for jibbers (rails, boxes, etc...), but absolutely sucks for all-mountain.
As for your K2 WWW, you have the Jib Rocker which is their higher profile rocker tech. You will be much better off with their All-Mountain rocker like in the Turbo Dream. I know you mentioned that you do park, but since this is your first rocker, a more low profile rocker would be a better introduction to this technology.
Burton's V-Rockers are inherently lower profile, so you'll be good with those as well. Ride's DH2 has a low-pro rocker too.