The very fact that it's near collisions vs direct collision. You're correct that having dedicated ASIC's does increase the hash-rate, and thus could lower the t

The very fact that it's near collisions vs direct collision. You're correct that having dedicated ASIC's does increase the hash-rate, and thus could lower the time-bounds. But the dedicated ASIC's are only really expanding the I/O interface to get more data in/out, and due to this have a much higher cost. The PoW system adjusts the difficulty based on the current distributed hash-rate, so an individual(or pool) is operating in a percent range of the total hash-rate. To analogize the two, properly, you'd have to set the PoW system to the highest difficulty, and keep it there for every individual password you want to check. Also the scrypt currencies have a fixed memory bound, AFAIK. While use in password cases, "could be" modified in the middle, doubling the required time-bound.