Well, i've bin doing ToGC10 yesterday late, and arround 34% HP I start lifetapping me to ~80% mana (Lifetapping to 100% is a risk). But, when we hit anub arround 10%, im mostly out of mana, or quite low. Lifetapping at that moment leads to a death most of the time.
Do you other locks have problems with your life and this phase?
(Setup of healing is an holy pala, and a resto druid)