So far I've yet to see a presented problem; only explanations why SoP is even usable in the first place.
"The problem is that this single card acts as a stallbreaker in and of itself." This is, of course, false. Just like Fractal, which breaks stalls a lot better due to not being vulnerable to either CC or PC (but is vulnerable to QC), it requires good enough creatures. Too low HP and you -should- pay for it, unless your opponent is a dunce.
So the only argument left that bothers me is how it interacts with Burrow. I agree that's a powerful mechanic, solely because of how good SoFo Grabbows and other speedbows are. I wouldn't mind if it changed, even though Nova remains the fundamental problem at hand.
In the end, this card isn't close to OP, but I know you mostly started this topic on principle because you want to balance all cards, one at a time. My response to that was that it'd take way too long. Zanz adds new cards to change the meta instead for a reason. In this case we need more PC, but that was already true before SoP anyway. That explains my vote, of course (add more PC).