Although irrelevant to your purchase, the Madshus skis like the Voss and the Glittertind have a different waxless pattern as the Eon, Epoch and Annum.
The MGV+ looks like this:
And well you know what the Omnitrack looks like on the bigger ski:

Again really tough to directly compare due to the camber difference, but the Omnitrack climbs much better IMO.
As far as the Fischer losing grip - I was really 'bouncing' the ski to try to set it and I'm sure I was getting it flat, and it just doesn't have the grip in those conditions that the Madshus had.
On to your questions regarding your next ski:
I'm a little fuzzy on camber and a half because I've never had one or felt one. So I might not recognize it unless someone pointed it out to me. I know the Eon claims to be that, but I've never played with them to compare.
That said, I'm 99% sure the Glittertind is a true double. Why? It is so darn stiff in the last 1/4" of deflection that you'd almost need a vice to get ski to touch ski in the middle... and that has always meant double camber to me. E99's are the same. So it appears that both have a defined wax pocket.
In regard to the Voss - I have not tried them but it seems consistent in that the Madshus skis tend to be softer all around that the Fischer counterparts. I actually like the extra stiffness for kick and glide (as long as I can set the pattern or wax, but I'm over 200lb so even on a long ski that's not usually an issue). For me, for turning, again not a huge issue because I have enough weight to deflect either ski.
As much as I like the quality of Fischer skis (and some of their attributes) - if I was going to buy another ski tomorrow from the backcountry lineups, I'd probably buy a Madshus first and then maybe consider a Fischer if I found a pair for a screaming deal. I only bought the E99's and S bounds because I found good deals on them.