Think Tank Retrospective 20 bag
I have a number of bags from Think Tank SLR holsters up to f.64 monster bags. Recently I started carrying a Nikon D7000 with a battery grip AND a 70-200 f2.8 attached. I couldn't find a good fit in any of my bags.
I spent a lot of time reading reviews and visiting the local camera stores to look at bags. I ended up with the Think Tank Retrospective 20. It seems quite expensive for a padded denim bag but it works as near perfectly for carrying a DSLR+battery grip+mounted 70-200 f2.8 lens as I could find.
The camera body + mounted long lens fits nicely in the center divided compartment with two lenses off to one side and my flash and odds and bits in the other compartment. There is still plenty of room for other large flat pieces in the outer pocket plus an inner pocket for more fragile stuff. There are two outer side pockets, one of which I use to hold a very large monopod. With everything in the bag it is quite heavy but the strap is comfortable and can be extended to wear cross style.
One difference in this bag versus others I looked at is that it is longer than it is wide. That makes it (for me) more comfortable to carry since it doesn't jut out. It is also deep enough (front to back) to hold the camera (lens side facing down) with a battery grip attached. Most of the other bags I looked at couldn't hold the body with big 70-200 f2.8 attached in one direction with enough width to accommodate the battery grip.
Although the bag itself is not waterproof it comes with a rain cover.
The main con to this bag is it is expensive and I couldn't find a used one. $167+tax for a camera bag is a lot of money to me but hopefully I'll use this one as long as I've used my canvas Lecia bag from 1978
If you need a bag to carry a dslr with a fast telephoto attached give the Retrospective 20 from Think Tank a look.
Colossians 3:2 -- Set your mind on the things above, not on the earth below