re: When will leagues start going with the 2 QB format?

I can't argue with that. If you like points, it's definitely fun. I did once, maybe twice... just not my thing. I'd do it once in a while just to change things up, but I certainly wouldn't make it the standard.

With rb tandems becoming more prevalent and rb values dropping, what's next? PPC?

Want to increase the quarterbacks value, play in a standard. You'll see those quarterbacks come off the board much quicker.