ya, they only block for X amount of damage or for 30 secs which ever comes first. So if you can do their whole amount of HP + the full block amount in one hit you would kill them in that hit.
Higher levels block more damage so as the monsters hit harder it blocks about the same percent. Or at least that is the basic idea behind it.
And for the part about them removing it, they took the numbers off almost all our skills and abilities.