Not really. Congress has the constitutional authority to dig into justice department corruption - which has been clearly demonstrated by its actions. The justice department isn't its own branch of government. Its head, the POTUS, can direct it to cooperate with its oversight. To claim obstruction of justice sets the DOJ as the law unto itself where no one can hold it accountable.
Please take this as just my personal opinion, but I believe this is where we are. Trump has the unlimited Mueller investigation hanging over him, ready, willing and able to turn every move Trump makes into a case for obstruction. With the press and most of the DC old guard is solidly behind him, Mueller doesn't have to worry about the weakness of the case; he will receive full throated support regardless.
That's just my POV. YMMV.