A friend of mine discovered that using an elixir called [Gift of Arthas] will give your attackers a 30% chance to inflict themselves with a disease that lasts 30minutes.
Pretty much means you drink the elixir, which lasts 30minutes, and during that time, any melee attackers that hit you have a 1/3 chance to catch this disease.
Your [Death Strike] ability heals for 50% damage dealt per disease on the target, so this elixir's disease would add 50% to the healing done on that ability. An easy way to test, (which I have) is to allow a mob to attack you until only the elixir's disease is on the target. Then proceed to death strike it once, and watch as you get healed for 50% of the damage you dealt. Proof: if you have no diseases on the target, you will not be healed.
As for where this would come in handy, as a tank, you have a higher amount of damaged self-healed, and since this can also be spread through pestilence, you will potentialy be able to pull out more threat.
1.Drink [Gift of Arthas]
2.Get hit by melee attacks until your target has the disease
3.Apply all the diseases you normally use
4.You now have obliterate/death strike/heart strike bonus damage from that third disease
5.Profit
by Apotheosiss