So with the
5.1 PTR notes being posted, I figured it wouldn't hurt to confirm what were real changes and what were just tooltip clarifications just to make sure. I didn't test Blood Boil and Soul Reaper because we already knew they got hotfixed, but I did test Death Strike, Heart Strike, Rune Strike and Death Siphon.
Heart Strike: Has been hotfix nerfed to 105% wep damage + 572.
Rune Strike: Is doing 165% weapon damage for me while the ingame tooltip says 175% and the 5.1 tooltip says 160%. Not sure where the difference is coming from but it is closer to the 5.1 value atleast.
Death Strike: Seems to be doing ~265% weapon damage + 1350 (not exact, but around that ballpark) which is lower than the 5.0 tooltip from MMO-C but much higher than the new datamined 5.1 version.
Death Siphon: Using 5.1 values already.
So it looks like that indeed most of our abilities already were hotfix nerfed and my guess is that the 5.1 Death Strike tooltip is datamined wrongly (I remember MMO-C having trouble differentiating between the Blood specific Death Strike and the Frost/Unholy one and the 5.1 tooltip actually matches for the DPS specs - which is probably not a coincidence).
I don't know when all these hotfix nerfs went through, but I have a suspicion it happened shortly before this raid reset.