The wildcard for me is that there are so many different kinds of hiking photography:
1) Backcountry hikers = it's all about keeping size and weight down. That says 1 body and 1-2 (small and light) lenses, possibly a tripod for astro if that's your jam. Pack a 40 pancake (or possibly a 35 f/2 IS) and an 85 f/1.8 or 100L.
2) Day hiking with non-photography friends/family = it's all about running and gunning and not slowing the convoy down. Pack a zoom. This is where the 24-something zooms are gold if you prefer landscapes and the 70-something or 100-400 zooms are great for wildlife. Pick one and stick with it. Keep it simple, stick and move.
3) Day hiking with other photographers = bring the kitchen sink. You're with other people that are down with a 20-30 minute setup of tripod, ND grads, etc. or will wait at the great vista for the best light.
I'm always stuck with #2, so it's almost always the 24-70 f/4L IS on my 5D3. No time to change lenses, absolutely no time for tripods.
Agreed that hiking means different things to different people!!
As someone who is usually in group #2 but from time to time in group #1, I generally agree with what you say, although I have found a 6D + 24-70/4L IS on a Black Rapid Sport strap can work pretty well for a group #1 trip as well as a group #2 trip. (Of course, there may be particular trips where 24-70 really isn't the focal length range you want.)
I am sure not everyone will agree, but I think the 24-70/4L IS is one of Canon's best landscape lenses, certainly in the hiking context. If you think about it:
24-70 is a pretty useful range for landscapes (yes, wider can make for spectacular shots but you need to have the right scene for it, plus of course stitching a panorama can be an option if you don't have a lens as wide as you'd like with you);
24-70/2.8L II is bigger and heavier, query if it is any better optically at the sort of aperture you would commonly use for landscapes, no IS, and it doesn't have the 4L IS's macro mode for things you spot while on the trail;
24-105/4L IS has the advantage of longer reach (which could be a real advantage sometimes), but at the expense of the macro mode, some IQ (eg not as sharp, more distortion) and a little bit of size and weight.