In PvE gameplay, the Swordmaster is first and foremost a tank. Their job is to gain agro on one or more mobs and hold it, ensuring that other players are not being attacked. To do this, a Swordmaster must be skilled at more than simply spamming high-threat skills such as Graceful Strike. They must also know how to position a mob and when to use their defensive skills to reduce incoming damage.
The Swordmaster excels at both multi-mob tanking, and tanking without a shield. However, just because a Swordmaster can tank without a shield does not mean that they should. Depending on Mastery spec, there are some options that will only be available when using a greatsword, and some options that will only be available when using a shield. Currently, however, the benefit of being able to block far outweighs those aika gold gained from using a greatsword; this is because in Aika, blocking defends against all attacks ranged and magic as well as melee.
For those players who have picked a Swordmaster, yet lack the zen required to be a worthwhile tank, fear not. For Swordmasters are able to pump out respectable damage with their greatswords and the help of mastery points spent in the Path of Khaine and the Path of Hoeth.