There are 2 common builds for the assassin that are considered viable. One is the elemental damage based trap assassin, who combines pheonix strike and high level lightning senturies to massacre large packs of enemies with arrea effect attacks. This type of assassin typically uses a claw/shield gear selection. Very good and killign large packs of physically resistant enemies, this build had trouble against strong single targets.

Antoher popular build is the melee assassin, who combines high levels of claw mastery, tiger strike, and dragon claw, with burst of speed and the death sentury trap skill to become a virtual whirling dervish of damage. Begin the fight by laying out several death senturies, then sink your claws into the nearest monster, as it dies, it's body will explode, dealing massive aoe damage to it's friends. As more die, the body explosion chain reaction will gain momentum, until you massacre the entire pack. This build is excellent for destroying bosses, but is not quite as successful at destroying large mobs of creatures as the elemental trap assassin.

When hunting for equipment, you will want to get as much damage reductiona and elemental resists as you can manage. Thanks to her leeching martial arts styles, an assassin does not need excessive ammounts of life or mana steal to remain effective. A martial arts assassin will probably want to very hgih damage claws - natalya's mark and bartuc's talons make powerful weapons, as do Fury runeword feral claws. A trap assassin will probably want a claw shield style - stormshield and bartuc's talons work very well in this regard, giving you alot of bonus to skills, resistances, and even phjysical resists.

Remember ot use your merc! A properly equipped holy freeze merc - using the blackleech blade bill can literally cripple an entire screen of enemies, becomming the ultimate crowd control. Cutting the monsters attack and movement speed to a crawl, while cutting the melee damage they deal in half allows your assassin to safely wade into the forray, and begin to deal death and eviceration with little fear of getting mobbed. You can use dragon flight to instantly teleport your mercenary to you if he gets stuck or mobbed.

In boss fights, once your have dispatched the unique monster's minions, an assassin is wonderful as ripping it to pieces. An assassin's strength is 1:1 battles, and they are quite capable of standing toe to toe with even the three brothers, and dicing them into demon chow very rapidly. Even a frenzy barbarian will have a hard time outpacing the single target damage output of a melee assassin.