Very confusing with multiple devices, and causing duplicate contacts

I have two iMacs running Lion, and an iPhone and iPad each with iOS5. I thought that if I set my iMacs to have the Cloud as the primary account, that once I deleted duplicate, triplicate or quadriplicate contacts at iCloud.com, that would trickle down to all my other devices. But that doesn't seem to be happening. I did that at iCloud.com, but notice my Mac here still has the multiple contacts. My iPhone seems to be OK for now, but we'll see if that stays OK too. How to I make sure that this doesn't happen? It seems there should be a bottom line primary account, like iCloud.com, that should rein supreme, and once that's done and then all devices are set to sync with it, any changes to any of these devices will then merge into iCloud.