As of the cosmic-tweaking patch we got this Tuesday, the power Life Essence is no longer healing other players at user-value when the "if the target is poisoned" condition is met. While the healing is still increased on allies when the condition is met, it is, like other drain heals, supposed to heal allies at the same value it heals the user.
For example, a character I have with a sizeable amount of Presence in Support role with the power is healing herself for +446 per tick. The healing for allies without a Poison on the target is +223 per tick. However, instead of increasing to +446 per tick on allies once the target is poisoned, as drain heals are meant to do, the healing is only increased to a measly +242 per tick.
I tested whether this was specifically an issue because of advantage combinations and found no evidence of such, and as there was no official word on this value change, compounded with the fact Mind Drain and Life Drain both are still increased to user-value when their conditions are met, I am led to assume this is unintended and thusly a bug.