I don't entirely agree. The only time I had issues with my team's transition D is if I leave it on man to man. Since patch 2 or 3, I can't remember, 2-3 zone and Half court press pretty much eliminate any issues I've had with bigs walking up the floor and killing me from the arc. Once the team settles into their offense, man to man (or a zone) is the way to go, but using it for transition D has always been horrible.
If THAT'S what you mean, then sure I agree. Man to man defense is terrible for transition D.
Fastbreaks can be hit or miss, but I assume most people aren't talking specifically about how overpowered a Russell Westbrook type player is in the fastbreak. Because... he's overpowered in real life.