This is one of, if not the most common warlock arena build.
This is known as the Soul Link build. Basically you get the survivability of the demonology plus the very useful drain life features in the affliction tree. It is important to note that the idea of this build is to outlast your opponents. Your dps is very low so this build will be fairly useless in 5v5 Arena and large battlegrounds. However, your survivability will be above all other classes.
