FB I do agree isn't as strong as I'd like it to be. In my mind, FB is a must on cp Petal and Skye. With Petal's minions able to land more dmg and Skye's A able to hit enemy heroes more easily. FB on Samuel is also really good for his A, whether to escape or to chase someone just within your range. On Riem, however, Fb isn't something I'd usually buy. BM and Eve are some good items on him, but I do pick up a FB at times if I'm having issues with people escaping me or I'm behind and can't...

I myself have also won many 2v3 matches, some even in ranked. It kinda depends on who you're playing and if the other person on your team wants to give it a try. I always try to play a 2v3 until completion, win or lose doesn't matter to me. In the end I just see it as practice. When a teammate goes AFK, don't surrender.