Full hybrid builds in the stickyFollow

So I was reading the sticky trying to figure out which way to go as I level when I noticed something odd. In the talent selection section the sticky mentions picking a primary tree and then a secondary tree, and how it is very unusual to go higher than twenty points in the secondary tree. Then in the talent section it mentions two hybrid builds that violate this rule, 31/30/0 and 0/30/31. The 0/30/31 build I have seen mentioned on WoWwiki in the articles on Moonglade Rainment and Warlord's Sanctuary, but this brief aside in the sticky is the only place I've seen the 31/30/0 build. That said, everything I've read seems to suggest that full hybrid builds are being pushed out by more specialized builds and a lack of itemization, at least in PvP and raiding. So my questions:
1. Are these viable builds for endgame raiding or heroics or PVP?
2. If they are not viable builds should they be mentioned in the sticky, or should they be mentioned but in the context of why they are not viable?
3. If anybody has experience with the 31/30/0 build, could you tell me about how it plays and how you go about gearing it? It doesn't look like there is much synergy between the Balance and Feral Trees (aside from the 20% boost to intellect), but I don't have the experience to really say (and it's like a song that won't get out of my head).

Any hybrid involving Feral is going to be gimped as cat DPS without mangle is 30% or more below what you would have with mangle.

Balance/Resto hybrids certainly can work well though.

With the 31/30 Balance Feral split, presumably, you are DPSing as Moonkin. So the question there is how gimped is your bear form when you only going thirty points in?