I think tanks taking Heart Strike is rare, also it would be even more reason to ditch Blood Boil in favor of it.
And I doubt Blood Boil will help with threat from Cleave goes brrr
Blood tank threat is dire, because you waste Blood rune on Blood Boil and expect it to help with aoe threat. Cleaves and divine storms, sounds bad, but then you realize that dnd+diesaeses perfectlyy keeps mob on you and those 1-3 "spiky" targets you can manage by switching targets. Why cast Blood Boil and in the end put extra little threat on that one mob you actually need more threat on? You can just switch to that mob and HS/BS.
I guess that depends on player.
Idk what kind of spec you use, but I usually go for spec like this to level/entry farm dungeons at 80:
https://wotlkdb.com/?talent#j0ERqIhc...g0xZcgh:mip0mV
First pick Blood tree, then Unholy tree, then Frost tree.
Things like extra 3% spell hit, 15sec CD on DND will make you way more realiable and smooth in dungeons. Death Rune Mastery is grand, it opens up insane flexibility and boosts your threat potential into sky, you get 2 extra(optional) IT casts each Rune cycle. Extra duration on Diseases will let you reliably maximize Runes and refresh with Pestilence, maximizing Death Rune Mastery.