No, it was not common practice. And, yes, Clinton did fire all the district attorneys general around the country. That was unprecedented. And when W came into office, he left all Clinton’s appointees in place, which greatly weakened what he could do.
I think Clinton fired all of the US Attorneys. Bush fired a few and then he was excoriated in the press, which had given Clinton a pass. IIRC
...once again proving that the POTUS is just the prime puppet of those who are TRULY in control. We are too caught up in the chess game to notice who owns the game.