Samurai is a rare hero and deals great damage.
Warrior: A strong warrior who terrorizes his opponents.
Soul skill: Mighty Strike: Deals X true damage to an enemy.
Deadly Cut: Deals X damage with 3% critical chance (12% maxed).
Warrior's Challenge: All enemies must attack samurai briefly, samurai gets 3% (11% maxed) armor.
Finishing Strike: Deals heavy X damage to an opponent X% more if target below 22% (40% maxed).
Fearsome Visage: Stuns target briefly.
Demon Shout: Lowers all enemies' attack by 23% (50% maxed).
Passive skills: Edit
Way of the Warrior: Increase attack and damage.
Great Resolve: Increase magic resist by 8% (28% maxed).
Honor Above All: Increase armor and defense.
There are a lot of ways to go about him. Demon Shout is basically a necessity, since it drastically lowers all enemies' attack, which will help your tank. Pre-55, he doesn’t have the potential to be used for damage. As a result, you should use Demon Shout and Warrior’s Challenge as his active skills and both defensive passive skills. Fearsome Visage is usually slotted in for the stun or an attack to add a bit of extra damage to the team. At level 55, you unlock access to the Reaver's Blade. This is a hugely offensive weapon. As a result you can change up the skills to a more damaging setup and wreak havoc. It’s still viable to use him as a debuffing tank, but you now have this viability.
For weapons, you generally want to aim for more defensive weapons. The Dominator has the highest defense out of all his available weapons pre-55, and Accursed Spark outdoes it at 55. At 55, if you want to go the damage route, Reaver’s Blade is pretty much unparalleled. Armor will likely come down to the defensive Chainskin or the offensive Wretched Chain, if level 55.
Samurai is among the best heroes in the game. He can be used as damage dealer, warrior or tank, with his Demon Shout a necessity. With its low initiative, it'll usually be the first skill your team fires. Demon Shout can actually pair nicely with the Paladin's Holy Shield, limiting incoming damage even more.