What seemed like what would not work in assassinating the mobs in Sharn content(R10) has been revisited and the DC number seems to be 125 Assassinate to work on the non death warded mobs. Consume works just the same but seems to sometimes not go off or gets delayed by 5 seconds or more or not go off at all.
I'd suggest having True Seeing and 100% Fortification bypass as well(though haven't tested without it, but have seen misses on rare occasion).