We don't know threat modifiers on them, and heart strike will only be relevant for tanking anyway. That may make a significant enough difference in and of itself.
Though it's a bit confusing that they seem to be prioritizing Death Strikes for tank purposes, what with the mastery bonus for the tree, yet Death Rune Mastery still converts the FU runes, not the B.
Edit: Seems like heart strike is getting adjusted or something as well, as your numbers don't agree with the ones on wowhead or mmochamp, and nor do either of those agree with eachother.
Edited, Jul 31st 2010 5:45pm by Norellicus