I wouldn't worry honestly. Nobody really plays Sacrificial Pact as it is a dead card vs 8 classes (and, no, not really worth it for the 5 HP heal by saccing your own Demons) and it doesn't really do much in the Warlock v Warlock match-up outside of the vs Jaraxxus case.
Basically, you don't play around the <0.1% chance.
If they want to nerf Ysera and Ragnaros then they should make it so that their effects proc at the start of the turn.
Do you lower their costs to compensate? Even then, they'd still most likely be unplayable if they were "hope you untap with it still in play." Like, Ragnaros as a big Demolisher is pretty bad. His pseudo-charge effect is what makes him good. If they're going to nerf Ragnaros, just lower his damage.
Though I don't see why they'd nerf Ragnaros.
The Sylvanas nerf they made is practically irrelevant. She will still get used in every control deck.
The one notable change is she may be removed from aggro/tempo decks that aim for turn 6-7 to be their finishing turns. Like, if she's expected to be a more control-based card, then it is more-or-less okay for her to be in most, if not all, control lists. There's really nothing wrong with some cards just being auto-include in certain lists. Sylvanas' issue was that she was auto-include in literally every deck.
...though, to be fair, Mind Control on an early turn is still just a super silly powerful effect. That may end up being adjusted somehow.
Eh, she can no longer be combo'd with brawl on turn 10 and she comes down a turn later. Hardly, an irrelevant nerf. I doubt this is the last we'll hear from Sylvanis though considering its power.
Can still Sylvanas + Shadowflame and steal Tirion / Ragnaros / Ysera / Giants!