I either read it hear or on LogicProHelp.com.
Someone suggested running Plogue Bidule- loading multiple instances of Omnisphere. So I tried it out and it worked like a charm- plus- it assigned each instance to a core- so this is a nice way to get full useage of your cores. I was able to play 2 Omni's loaded with the patches Deigo showed on his NAMM vidoes (basically 2 big multis). In Logic, this would just kill everything- as it all went to one core. In Bidule- I can get both cores humming. Definately worth checking out