Epeirus went to crap when Pyrrhus died.
I wouldn't quite say that. Epeiros enjoyed a brief resurgance under Pyrrhos' son, Alexander, who managed to conquer Makedonia from Antigonos Gonatas around 260 BC. Had he managed to hold onto it, I think Epeiros could have achieved hegemony over Greece. Whether they'd have faired any better against the Romans than the Antigonids is another story.