i just updated this page http://irowiki.org/wiki/Drain_Life
i always wondered why my absorb rates always different to what the wiki said. until i tested it myself and i found the real absorb value.
previously, on wiki, drain life has absorb rate of 10%, 15%, 20%, 25% and 30% for each level. While it is actually 14%, 28%, 42%, 56% and 70%.
That's why this skill is worth taking. I often healed about 15k when dealing 22k damage.