IMO ALL marine tanks have ick, period. If the fish are happy/healthy their immune sytems just fight it off, and you never see the signs of it. If they start getting stressed, or they're injured they have trouble fighting it off effectively, and then you see it.
The only exception to this that I can think of would be if you were to catch all your own fish/inverts, and harvest your own LR and coral, and QT them all one by one before putting them in your show tank. Since I haven't heard of anyone that can manage that I don't believe there is an ick-free tank out there.
The things I've read/heard about UV sterilizers basically comes down to if you run one high enough to kill ALL the ick, you've also just killed all your bacteria and phyto, which means your reef isn't gonna last long.
Of course this is just my opinion, but I think that QTing every fish/invert is silly because ick will still hitch on your rock/corals. I think that if you don't put obviously sick animals in your tank, maintain your water quality, and don't put animals that are not compatible in your tank, be it because of tank size, or other animals etc... you're unlikely to need to maintain a QT tank.
This of course mainly addresses ick, and not all the myriad of other parasites, or diseases our animals can come down with. If a fish appears sick, and I can remove and set up QT tank I will.
B