The Blood tree relies on a very simple set of moves to create a rotation from. You will always want both diseases active for the sake of buffing Heart Strike damage and Death Strike healing. After that, you will have two paths you can follow at any given time. Death Strike will be your tool to convert FU pairs into Death runes, but once they are Death runes you can choose to either us them for Heart Strike or Death Strike. Heavy use of Death Strike, even if glyphed, will generate a little less threat than Heart Strike unless you get high effective healing from its use. For this reason, in general, you will want to favor HS when you are at full health and only use DS on Death runes when you know you can get value from the heal.