Same experience here with 5D2 with raw capture It is just a "normal" shoot of a model in black dress outdoor at ISO100.
The red colour noise is so visible on the black dress without noise reduction! Had to dialup NR in LR so much that some detail of the dress is lost to completely remove the color noise... Sigh... if Canon can't do it at ISO100, forget about those ISO800 shots!
It is such a basic requirement!
When I first got my 5D2 I was so excited to finally play with what everyone was raving about.
I was not impressed from the first shot.
Raw noise levels were worse than my 40D and I had visible banding right smack in the MIDtones at low ISO! That was with the earlier firmware, 1.something, a version or 2 after they fixed the black-dot issue.
I should have sent the camera back but instead I parked it for about a year until, finally, later firmware versions mitigated the midtone banding and the camera was at least usable. If the shot didn't contain anything really dark the results really were actually impressive at that point and I used it for a lot of landscape and some low-light indoor event shooting. It was a pretty decent performer in its early days but it certainly left me disappointed in many ways.
Today I was out on a short hike and took only one camera; a D5100 and a few lenses, tripod and small white reflector to use when doing some close-up and macro shots on wildflowers and similar. I almost took the D800 as well but decided to try travel light and I really didn't think I'd need the extra rez. Mostly used a 105mm macro and mounted the cheapo 55-200mm kit zoom a couple shots where I needed some extra reach.
I could have just as easily taken a Canon Rebel, 100mm macro and something like their 55-2X0 lens or even their fairly good 18-200mm superzoom. But I now know better.
Since it was a bright sunny day and I was going to be shooting in the open and possibly in the wooded areas with a mix of sunlight and deep shadow there was no way I was going to use a camera that could not handle the dynamics of such a scene. The Canons stayed at home and the new puppy came along for the walk.
It performed admirably and obediently and I took 132 shots with raw files I can tweak as much as I'd like without any worry of pattern noise showing up to ruin the effect and I don't have to worry about using any NR and risk losing some detail. That's what I want from a camera and I found some that can finally deliver.
It's just too bad I had to alter my mfr allegiance to do so.