Yeah I was just looking at the 5d mark ii specs actually, and it seems to be comparable to the 6d for my uses... con is it's heavier, and not as good in low light; but, for everything else the same. 5dmk3>6d>5dmk2 (barely)
I would take a 7D combo on day hikes, having two cameras is an advantage and disadvantage I think.
However, I would definitely leave the 7d and just take the 6d/5dmk2 for multi day trips into the backcountry (or hopefully will sell some prints and save up for 5dmk3). All these cameras have good enough weather sealing as long as I'm careful I'll never have to deal with breaking a body hopefully .
Any more opinions on a 5dmk3 versus 6d/5dmk2 + 7D combo?
The 5D2 is a warmed over 5D, I would strongly suggest you stay away from that. The 6D is more closely akin to the 5D3 than the 5D2. Push the 5D2 up into the higher ISOs, and the newer bodies are better, even APS-C.