I found interesting information that confirms that bladesman is a waste of a three perk investment. At rank 3 it provides a 20% chance of 50% critical hit damage, however +50% is only on the base damage of the weapon. The highest base damage weapon is apparently 21 so rank 3 bladesman will only provide on average 2.1 extra points of damage. Please note that upgrading via smithing, potions, perks etc do not increase the base damage of the weapon.
Therefore, Bladesman is probably one of the worst perks in the game.
Source: http://www.uesp.net/wiki/Skyrim:Bladesman#Bladesman
