*sighs* the main trouble is not about samurai vs dark knight, but samurai vs warrior.
i will go farer since some people like to avoid the main trouble.
for make a tank into a game viable and balanced you need to have con and pro.
for a two handed weapon tank, you loose the resistance of a shield, then you go either with magical buff or hp pool. strangely we already have the two... for the hp pool you do have the warrior... and the magical one it will be the dark knight (even without know the jobs, yoshi-p have already explain that the jobs will be based on the magic)
other point that seems to be avoid totally, parry don't nullify damage... when you parry you still take damage, make it more dodge based? we already had this talk with the ninja tank thread. if a jobs dodge all, it's overpowered, if it don't dodge enough, it will be underpowered.
samurai tank can't bring anything new to the tank role soo far. exept new mechanic for deal damage.... that are more interesting to develop for a damage dealer.
and i'm talking about the game, not the irl... weapon damage is what count, the animation are only for the eyes... what they do is the important. that why summoner can't really be a pet jobs like some ask, because it will not be different of the black mage... we are talking of game, not irl and that why soo far, samurai will be too similar of the warrior for be a decent choice.
counter can't be used as a particularity... because you can't counter magic in the game, you can't block, parry magic, you can only dodge it. other point, the paladin already use a country skill, even if it's under used it's already in it skill. a reactive tank is nice when you have a huge hp pool and have regen skill... or the jobs will be soo much unbalanced.
because if it's like what you offer, he will have not a lot of life, not a lot of damage reduction... for get.... a country strike that will only work on physical attack. even if you put all the mechanic on the parry.... parry can't reach 100% of chance, and even if it's 100%, parry damage nullification rarely pass the 24-25%.... why take the samurai? i means, the paladin already have a passive -20% damage that can be boosted by the block, parry...
that the whole point... the jobs will bring nothing new and will be a pain to balance even if you put it on parry mostly, even if it's a jobs based on dodge it will be worst...