This is in fact an interesting question, and I mean for me, as well as others.
Because it is quite clear that the power of compassion is very far reaching, if not from personal life than from the texts. And as for the instructions in developing compassion, it is recommended that one develop it limitlessly. So boundaries on compassion are not really recommended, at least in the instances in which one is having it. But as to whether there are some moments that are proper for compassion, and others more wisely directed, this too is an interesting question. I'm not qualified to answer and I figure that sometimes a person can almost be wise to "OD" on empathy whereas at others they would be wiser to do some other practice.
I don't want to draw the thread amuck, but might there be room for discussion on the differences between empathy and compassion? Empathy is almost closer to amicability, or friendliness, but certainly has a feeling quality.
I would say though, that at the very least, empathy is also a good quality or technique in favor of dominance.