with regard to proccing the Steal or drain life. i have a ds on my AIEW, my hitter and my thief and they all proc the drain for less than desirable damage. especially if the target has necro resist at all. vs players it does like 50-80 dmg and vs mobs it can do as much as 3-400 or as little as 45 in my anecdotal cases.
PS: t mask and HoS proc seem a bit "off" tm doesnt work at all and HoS never seems to proc. tried on 10 base endur and 20 base endur toons with full max gear( expert level)