Drain-tanking refers to a Warlock's tactic. It is the process of using Drain Life on your target to keep you alive while damaging the target. In most cases, this is coupled with the heavy use of DoTs on them. In the 2.0 patch, Drain Life was buffed twice, making this tactic even more appealing. Both its gain from spell damage equipment was drastically increased, and the respective talent (previously Improved Drain Life, afterwards Soul Siphon) grants a lot more damage increase.