We definitely feel the need for warlocks to gain some sort of active defense so we don't have to try to balance them around the assumption that they're "tanking" melee classes. For example, an idea we're running with internally is the concept of a warlock being able to cast a spell that places a circle of demonic power on the ground. The warlock would be able to teleport to this location from within a relatively short range (ie: 40 yards), and would also be able to summon demons more quickly if they're standing within the circle.
Blizzard