What would you do as the pitcher in this situation?
The runner on third is taking a secondary lead down the line on the pitch. On a comebacker, you are looking the runner back, no? If the runner freezes after taking his secondary lead, he is pretty far down the line and you can run at him and make him commit to a base, and likely will have him in a pickle.
If he breaks for home, I say there is no way he is safe unless it is a slow roller, like a swinging bunt or something. But on a comebacker, he isn't scoring unless it's an errant throw.
Even if there are two outs and the pitcher has no need to look the runner back, the runner does not need to break for home right away, because he is only going to score if there is an errant throw to first. The runner at third can easily score after an initial step back toward third and then break for home once the pitcher begins his throw to first.
Now, let's say there are less than two outs; on a comebacker, there is definitely time for a DP, right? But does the pitcher have time to look back the runner before making the throw to second? I say yes. So, I believe the pitcher's first priority is to always look the runner back at third. What if the runner on first was stealing on the pitch? The pitcher will have to make a judgment call as to whether he can get him at second now. If he looks the runner back at third and the runner on first is stealing, he has to go to first (unless there is a play at third due to the runner straying too far).
Anyone with me on this?